This was CNBC's live blog tracking developments on the war in Ukraine. 

Russian President Vladimir Putin has moved his longtime ally Sergei Shoigu from the defense ministry to Russia's powerful Security Council amid a government reshuffle.

Russian economist Andrei Belousov is set to be Russia's new defense minister, while Shoigu will replace Nikolai Patrushev, another long-standing Putin ally, at the Security Council. Patrushev will be given another role, the Kremlin said.

Shoigu had headed the defense ministry since 2012, going in to the role with no military experience, and oversaw Russia's invasion of Ukraine in February 2022.

Putin has remained loyal to Shoigu, although Russia's military leadership during the war has been criticized by some Russian commentators, the most high-profile of whom was Yevgeny Prigozhin, the head of the Wagner Group of Russian mercenary fighters. Prigozhin died last August in a plane crash; the Kremlin denied any involvement in his death.

The appointment of Belousov, former minister of economic development, is bound to raise eyebrows in military circles but comes as Putin looks to cement Russia's economy on a war footing and defense spending surges.

In other news, Russia's Defense Ministry on Sunday claimed more advances in the Kharkiv area of Ukraine after Russian forces launched a new offensive in the northeastern region.

Ukraine says it prevented Russian 'terrorist attacks' in Kyiv on May 9

Ukraine's security services on Monday said they had prevented "terrorist attacks" by alleged Russian agents in Kyiv that were meant to take place on May 9.

Explosive devices were meant to be detonate in several locations in Ukraine's capital Kyiv, including shops, the country's security services said in a Google-translated Telegram post.

"Improvised explosive devices were disguised in tea packages. They consisted of a timer, a detonator and plastic explosives with an incendiary mixture that was supposed to cause large-scale fires," the post said. The explosives were meant to detonate during peak hours, it added.

Explosives were allegedly also meant to be installed in a car that was to be parked near a popular cafe, the security services said.

Ukrainian security services used counter-intelligence to identify the man behind the planned attack, they said in another Telegram post.

"He personally gave instructions to the recruited agents and even recorded video instructions for installing an explosive device in one of the stores of the same chain in the Moscow region," the post said.

The alleged Russian agent had also planned an attack that was meant to take place in February, which was also thwarted by Ukrainian security services, they said.

Ukraine's Office of the Prosecutor General on Monday said two people had been detained regarding the attempted attacks. One was charged with treason and attempted sabotage, while the other was charged with "an unfinished attempt to commit a terrorist act," the office said in a Google-translated Telegram post, adding that investigations were ongoing.

Russia's Foreign Ministry did not immediately respond to CNBC's request for comment.

— Sophie Kiderlin

Russia has 'partial success' in Ukrainian town near Kharkiv, Ukrainian military says

Russia has had "partial success" in Ukraine's Lukyantsi, a village near the city of Kharkiv where Russia launched a new offensive in recent days, according to the Ukrainian military.

"In the Kharkiv direction, the enemy does not stop offensive actions," the Ukrainian Telegram account for General Staff of the Armed Forces said in a post on Monday, according to a Google-translation.

The update said 11 attacks had already been carried out and two "combat clashes" were underway.

Russia had "partial success" in Lukyantsi, but was prevented from advancing, the military said, adding that Ukrainian forces were carrying out counterattacks. CNBC could not independently verify the developments on the ground.

Earlier in the day, Kharkiv regional head Oleh Syniehubov said Russia was attacking in small groups in an attempt to stretch the front line, Reuters reported.

— Sophie Kiderlin

Serbia reiterates support for Ukraine, but does not move on sanctions for Russia

Serbia on Monday reiterated its support for Ukraine, but did not appear to change its position on international sanctions against Russia.

Serbian Prime Minister Milos Vucevic met with Ukrainian Foreign Affairs Minister Dmytro Kuleba on Monday and discussed the global security situation and potential economic cooperation, according to a statement released by the Serbian government.

"Serbia is committed to respecting international law and the territorial integrity of every member state of the United Nations, including Ukraine. We are open to friendly discussions on all issues and at all levels," the statement said.

Serbia has previously expressed its support for Ukraine and has taken in refugees from the country, as well as providing humanitarian aid and committing to support Ukraine's re-building after the war. However, the country has so far refused to impose sanctions on Russia, which has raised tensions between Ukraine and Serbia.

— Sophie Kiderlin

Russian reshuffle shows it will 'try to scale the war,' Ukrainian presidential aide says

The changes Russian President Vladimir Putin has made to the country's government suggest that Russia will try to "scale the war," Ukrainian presidential aide Mykhailo Podolyak said in a post on Telegram on Monday.

"Russia is finally isolating itself and will try to scale the war, expand its formats, while simultaneously reconfiguring the economy to function in acute/deficit formats, which one way or another can ensure a sharp increase in the military component," he said, according to a Google translation of his post.

The reshuffle indicates that Russia is, among other things, moving towards "military 'communism'" to ensure there are enough resources for a never-ending war, aiming to curb corruption in its army, and that the influence of "traditional clans" is being redistributed.

— Sophie Kiderlin

Russian parliament approves Novak as deputy PM

The Duma, the lower house of the Russian parliament, on Monday approved the nomination of Alexander Novak as Deputy Prime Minister.

On Saturday, Prime Minister Mikhail Mishustin proposed to lawmakers to re-appoint Novak as deputy prime minister with additional responsibility for the economy, on top of his previous duties overseeing the energy sector and acting as Russia's point man in the OPEC+ group of oil producers.

— Reuters

U.S. sounds alarm as thousands in Georgia protest 'Kremlin-style' foreign influence bill

Thousands of people in Georgia's capital took to the streets on Monday to demonstrate against a controversial "Kremlin-style" bill that critics say could undermine the country's chances of joining the European Union.

The proposed bill calls for media outlets, non-profits and other non-governmental organizations in the country to register as "pursuing the interests of a foreign power" if they receive more than 20% of their funding from abroad.

It has been described as a Kremlin-style bill because Russia has previously used similar legislation to crack down on independent news media and activists.

White House national security advisor Jake Sullivan said over the weekend that the U.S. was "deeply alarmed" about democratic backsliding in Georgia.

Read the full story here.

— Sam Meredith

Russia and Ukraine release updates on 'dynamic' fighting in Kharkiv region

Russia said its forces had improved their tactical position near four settlements in the northeastern Kharkiv region Monday while Ukraine said it had deployed reserves to the area, where Russia launched a new offensive last week.

Russian forces have "improved the tactical situation and delivered strikes at [Ukrainian] manpower and hardware" close to Vesele, Neskuchne, Vovchansk and Lyptsi, Russia's Ministry of Defense said Monday according to a translated Telegram post.

The ministry said Sunday that its forces have seized nine villages in Kharkiv region at the weekend after launching a new offensive in the region.

The General Staff of Ukraine's armed forces said in an update Monday that "the operational situation remains complex and dynamically changing" in the Kharkiv region.

Combat operations are underway in several areas, the General Staff said, noting that Russian forces were conducting assault operations in a number of directions.

 Fighting is going on for the border town of Vovchansk, Ukraine's military said, stating that Russia had used "significant forces to attack the city in the composition of up to 5 battalions ... At present, the enemy has tactical success," it added.

"Measures are planned for the destruction of the enemy, which has wedged itself into our defence."

Reserves are being deployed to stabilize the situation, Ukraine said, but it added that one of its main priorities "is the preservation of the lives of our soldiers."

CNBC was unable to verify the battlefield reports.

— Holly Ellyatt

Nominee for Russian defense minister underlines need to take better care of soldiers

Andrei Belousov, the surprise choice of President Vladimir Putin to become Russia's new defense minister, said on Monday that soldiers needed better access to housing, hospitals and welfare benefits.

Belousov, an economist who previously served as deputy prime minister, underlined the need to take better care of Russia's soldiers in comments to a parliamentary committee, his first since Putin named him on Sunday to replace Sergei Shoigu.

State media quoted him as saying there was too much bureaucracy surrounding the payment of benefits to military personnel. There were also issues with housing and medical treatment.

"I think it's a mess when participants in the special military operation who come back on vacation are driven from civilian medical institutions to hospitals which are often simply overcrowded. This issue needs to be resolved," Belousov said.

The comments by Belousov, who has no military background, appeared aimed at demonstrating to members of the armed forces that he understands their concerns and will work to improve their conditions.

He was addressing the defense and security committee of parliament's upper house, the Federation Council, as part of a confirmation process for a new government line-up after Putin started his fifth term as president earlier this month.

— Reuters

Russia is ready if the West tries to resolve Ukraine war on the battlefield, Lavrov says

If Western countries want to resolve the Ukrainian war on the battlefield, then Moscow is ready for it, acting Foreign Minister Sergei Lavrov said Monday.

Speaking during talks in the Federation Council (the upper house of Russia's parliament) on his reappointment to the post of foreign minister amid an ongoing government reshuffle, Lavrov said "it's their right, if they want to be on the battlefield, they will be on the battlefield," news agency RIA Novosti said.

Lavrov was dismissive of a forthcoming peace summit on Ukraine that will be held in Switzerland in mid-June, and which Russia is not attending, likening the event to "a reprimand for a schoolchild."

Russia has not been invited to the summit but had already signaled it would not attend even if it was welcome to. It has said a peace summit without it is futile.

Russia's leadership has repeatedly warned of the possibility of a direct confrontation between Moscow and the West, threatening that World War III could erupt if Ukraine's Western allies send ground troops into the country.

— Holly Ellyatt

Two Americans, one Russian citizen reportedly among 20 detained in Georgia

Two U.S. citizens and one Russian were among 20 people detained at protests in Tbilisi while Georgian lawmakers were debating a "foreign agents" bill that has sparked a political crisis, Russia's TASS state news agency reported on Monday.

Georgia's opposition had called on opponents on Sunday of the bill to stage an all-night protest outside parliament to prevent lawmakers from entering on Monday.

Georgian Prime Minister Irakli Kobakhidze vowed on Sunday to push ahead with the law, after opponents of the bill rallied in one of the largest protests seen since independence from the Soviet Union in 1991.

TASS reported, citing witnesses, that police started to push the protesters away from the service entrances of the parliament building early on Monday, leading to some scuffles.

The "foreign agents" bill requires organisations receiving more than 20% of their funding from abroad to register as agents of foreign influence or face fines. The ruling party says it is needed to enhance the transparency of NGO funding and protect the country from outside interference.

Western countries and Georgia's opposition denounce it as authoritarian and Russian-inspired. Critics liken it to Russia's 2012 "foreign agent" law, which has been used to hound critics of Vladimir Putin's Kremlin.

The dispute over the bill has come to be seen as key to whether Georgia, which has had traditionally warm relations with the West, continues its push for European Union and NATO membership, or instead builds ties with Russia.

The EU, which granted Georgia candidate status in December, has repeatedly said the bill could jeopardise Tbilisi's further integration with the bloc.

— Reuters

19 dead and dozens injured after strikes on Belgorod, Russian officials say

Russian officials said at least 19 people were killed and 27 injured during Ukrainian missile attacks on the border region of Belgorod this weekend.

Belgorod Governor Vyacheslav Gladkov, governor of the region, said on Telegram that the bodies of 15 people had been recovered from the debris of a residential building that had collapsed following what he described as a "barbaric" Ukrainian missile attack. He said 27 people had been injured in the attack.

During separate shelling on Sunday evening, three more civilians were killed, he said, adding that one woman injured in an attack on Saturday had also died.

Russia's Ministry of Defense said Sunday that Russian air defense systems had repelled the attack, destroying six Tochka-U missiles, four Vampire MLRS missiles and two Vilkha MLRS missiles. "Fragments of one of the downed Tochka-U missiles damaged a residential building in the city of Belgorod," the ministry said on Telegram.

CNBC was unable to verify the report and there was no immediate comment from Ukraine. Both Moscow and Kyiv deny the deliberate targeting of civilians.

— Holly Ellyatt

Russia claims gains amid fierce fighting in northeast Ukraine

Russia's Defense Ministry has claimed more advances in the Kharkiv area of Ukraine after Russian forces launched a new offensive in the northeastern region.

The ministry said on Telegram Sunday that its forces had "advanced into the depths of the enemy's defenses" and had "liberated" the villages of Gatishche, Krasnoye, Morokhovets, and Oleynikovo had been captured in the Kharkiv region. Russia uses Soviet-era names when referring to Ukrainian place names.

On Saturday, the ministry said the border villages of Pletenivka, Ohirtseve, Borysivka, Pylna and Strilechna had been seized. It also claimed that the village of Keramik in the Donetsk region had been taken.

More than 4,500 civilians have been evacuated in the Kharkiv region after Russian forces crossed the border and launched a widescale offensive there last Friday. Questions are being asked as to why Russian forces were able to advance in the region so easily, but a Ukrainian government spokesperson told the BBC Monday that the villages that had been captured were long-abandoned "zombie" villages.

Russia wants to seize the region, which includes the second-largest city in Ukraine, Kharkiv, in order to create what it calls a "buffer zone" to protect its own border regions from Ukrainian attacks, which have intensified in recent months.

Ukrainian officials were widely expecting the offensive and have sent reinforcements to the area but President Volodymyr Zelenskyy on Saturday called for Western military aid deliveries to be made as quickly as possible. Russia is trying to make as many gains as possible before Western military supplies, as part of an unprecedented $61 billion U.S. aid package, arrive on the ground.

— Holly Ellyatt

Putin replaces longtime defense minister Sergei Shoigu

Russian President Vladimir Putin has moved his long-term ally Sergei Shoigu from the defense ministry to the country's powerful Security Council amid a government reshuffle.

Russian economist Andrei Belousov will be Russia's new defense minister, while Shoigu will replace Nikolai Patrushev, another long-standing Putin ally, as the secretary of the powerful Security Council — the body charged with advising the president on national security policy. Patrushev will be given another role, the Kremlin said.

Shoigu had headed the defense ministry since 2012, going in to the role with no military experience, and oversaw Russia's invasion of Ukraine in February 2022.

Putin has remained loyal to Shoigu, although Russia's military leadership during the war has been criticized by some Russian commentators, the most high-profile of whom was Yevgeny Prigozhin, the head of the Wagner Group of Russian mercenary fighters. Prigozhin died last August in a plane crash; the Kremlin denied any involvement in his death.

The appointment of Belousov, former minister of economic development, is bound to raise eyebrows in military circles but comes as Putin looks to cement Russia's economy on a war footing and defense spending surges.

Kremlin press spokesperson Dmitry Peskov said the appointment of a civilian to the defense ministry was rooted in a need for "innovation."

"On the battlefield today, the winner is the one who is more open to innovation ... Therefore, at this stage, the president has made a decision for a civilian to head the Defense Ministry," Peskov said, news agency Tass reported.

Russia's top general, the Chief of the General Staff Valery Gerasimov, will remain in his job, the Kremlin said.

— Holly Ellyatt