This is CNBC's live blog tracking developments on the war in Ukraine. See below for the latest updates.
Drones hit several buildings in Moscow early Tuesday morning, city officials reported, causing "minor" damage and two injuries but no deaths. Emergency services were at the scene, the Mayor Sergei Sobyanin said. Moscow's airports remained open.
It is not clear where the drones came from, but Russia's Defense Ministry blames the attack on Ukraine, calling it a "terrorist" act. A Ukrainian presidential advisor said Kyiv had "nothing directly to do with this," while adding that "of course we are pleased to watch and predict an increase" in such types of attacks.
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The drone attacks follow three heavy Russian missile and drone bombardments of the Ukrainian capital Kyiv in the span of 24 hours. The attacks began Sunday, on Kyiv Day, which is a holiday celebrating the city's founding.
The typical street festivals, concerts and parade that would normally take place on Kyiv Day were either canceled or significantly scaled back, with tens of thousands of people instead spending much of the days and nights since Sunday sheltering in the Kyiv metro.
Russia issues arrest warrant for Lindsey Graham over Ukraine comments
Russia's Interior Ministry on Monday issued an arrest warrant for U.S. Sen. Lindsey Graham following recent comments about the fighting in Ukraine, the Associated Press reported.
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Ukrainian President Volodymyr Zelenskyy's office released an edited video of his meeting on Friday with Graham, who said "the Russians are dying" and described the U.S. military assistance to the country as "the best money we've ever spent."
Graham appeared to have made the comments in different parts of the conversation and the short video by Ukraine's presidential office put them next to each other, causing outrage in Russia, according to the AP.
The Investigative Committee, Russia's top criminal investigation agency, moved to open a criminal inquiry against Graham, and the Interior Ministry issued a warrant for his arrest, the AP reported.
Graham commented on Twitter, saying that "to know that my commitment to Ukraine has drawn the ire of Putin's regime brings me immense joy."
"I will continue to stand with and for Ukraine's freedom until every Russian soldier is expelled from Ukrainian territory," he tweeted. "I will wear the arrest warrant issued by Putin's corrupt and immoral government as a Badge of Honor."
— Melodie Warner
Russia says it reserves right to take 'severe measures' after Moscow drone attack
Russia's Foreign Ministry said it has the right to implement the most "severe measures" after Tuesday morning's drone attack on Moscow that it blames on Kyiv.
"Assurances by NATO officials that the Kyiv regime will not launch strikes deep into Russian territory prove to be completely hypocritical," the ministry said in a statement.
"Russia reserves the right to take the harshest possible measures in response to the terrorist attacks by the Kyiv regime," it added.
A Ukrainian presidential advisor denied the government's involvement in the strikes, but said that "we are pleased to watch and predict an increase in the number of attacks." The drone strikes caused "minor damage" and two injuries but no deaths, Moscow authorities said.
The drone attacks followed three heavy Russian missile and drone bombardments of Kyiv in a 24-hour period that began Sunday, which killed at least one person, according to the city's officials.
— Natasha Turak
Russia says it will target Western weapons supply routes in Ukraine
Russia will target and strike any Western weapons supply routes it detects ahead of Ukraine's anticipated counteroffensive, Russian Defense Minister Sergei Shoigu was quoted as saying by state media outlet TASS.
Shoigu noted that Ukraine's Western allies are boosting arms deliveries to Kyiv prior to what he described as an upcoming "large-scale" Ukrainian offensive.
The defense chief said Moscow was imposing "effective fire damage on the enemy" and that Ukraine's Western-supplied arms would not change the result of his country's "special military operation," which is the term the Kremlin uses for its full-scale war in Ukraine that began in February 2022.
— Natasha Turak
'Let your houses burn': Wagner chief slams Moscow elites
Reported drones attacks on Moscow in the early morning hit some of the city's prestigious areas and high-end residential streets, including a part of western Moscow where Russian elite, including President Vladimir Putin, have homes.
The chief of Russian private military firm Wagner Group, Yevgeny Prigozhin, was quick to slam Russia's wealthy senior military officials, saying the attacks were their fault.
"Why the f--- are you allowing these drones to fly to Moscow? Who gives a s--- that they are flying to your homes on Rublyovka! Let your houses burn," Prigozhin wrote on his Telegram account.
The suburb of Rublyovka is home to many of Moscow's wealthiest figures in business, politics and culture. Prigozhin has long been a vocal critic of Russia's top military brass and senior officials, who he accuses of corruption and of neglecting ordinary Russians, particularly those fighting on the front lines in Ukraine.
Wagner Group spearheaded some of the deadliest fighting in eastern Ukraine, particularly in the bloody battles for the city of Bakhmut, suffering heavy casualties.
— Natasha Turak
Ukrainian presidential advisor: We are 'pleased' to watch drone strike on Moscow, but 'have nothing' to do with attack
A Ukrainian presidential advisor denied Kyiv's involvement in a drone attack on several buildings in Moscow on Tuesday morning, but admitted that his government was happy to see it take place.
"Regarding the attacks, of course we are pleased to watch and predict an increase in the number of attacks. But of course we have nothing directly to do with this," the advisor to the head of the Ukrainian presidential office Mykhailo Podolyak told YouTube channel the "Breakfast Show," according to Reuters.
Russia's defense ministry called the drone strikes a "terrorist attack" and blamed Kyiv, saying that the offensive involved eight drones that were all shot down. Moscow authorities say there were no casualties and minimal damage was sustained, while some residential buildings were evacuated. CNBC has not been able to independently verify the information.
The strikes on Moscow followed an intense period of three separate heavy Russian drone and missile bombardments of Ukrainian capital Kyiv within 24 hours. The round of hostilities began on Sunday, May 28— Kyiv Day, an annual celebration of the city's official founding.
Attacks on Moscow are rare. On May 3, two drones were intercepted by Russian defenses above the Kremlin in what Russia's government says was a Ukrainian assassination attempt against Vladimir Putin, even though the Russian president was not there at the time. Kyiv has denied involvement.
— Natasha Turak
Finland hosts NATO exercises for the first time since becoming alliance member
Finland is hosting NATO exercises for the first time as an official member of the alliance, along with Norway and partner country Sweden.
It kicked off the event on Monday. NATO's Arctic Challenge Exercise, which this year is planned and directed by the Finnish Air Force, runs from May 29 to June 9 and has taken place every other year since 2013.
"The Arctic Challenge Exercises is part of the NORDEFCO cooperation between Finland, Norway, Sweden, and Denmark. Their Air Forces regularly carry out combined air combat-related Cross Border Training operated from their home bases," a description of the event on NATO's website read.
"The purpose was for the three Nordic nations to practice together and across their countries' borders," it continued. "Since then, the exercise has grown to include even more allied nations. It is a unique opportunity for nations to be practicing across larger training areas and with other aircraft."
— Natasha Turak
Russian defense ministry blames Kyiv for 'terrorist' drone attack on Moscow; Kyiv official denies involvement
Russia's Ministry of Defense accused the Ukrainian government of being behind a drone attack on Moscow that it said was intercepted, and caused no casualties but left minor damage.
The ministry wrote in a post on its Telegram channel:
"This morning, the Kyiv regime has launched a terrorist drone attack on the city of Moscow. Eight aircraft-type drones were employed in the attack. All enemy drones were downed. Three of them were suppressed by electronic warfare, lost control, and deviated from the intended targets. Five more UAVs were shot down by the Pantsir-S SAM system in Moscow region."
While the ministry said eight drones were involved in the attack, some Russian media sources say the number of drones was as high as 30.
Ukrainian presidential advisor Mykhailo Podolyak said in an interview Tuesday morning that Kyiv "has nothing directly to do with this."
— Natasha Turak
Moscow buildings hit by drones, city's mayor says
Several buildings in Moscow were hit by drones, the city's mayor reported early Tuesday morning.
"All emergency services of the city are at the scene of incidents," Mayor Sergei Sobyanin said in a statement, adding that the drones caused "minor" damage and no deaths.
Russia's Defense Ministry says the attack was carried out by eight drones and that all were shot down. The ministry accused Kyiv of being behind the attack. CNBC has not been able to independently verify the information, and Kyiv has not responded to the charge.
Russian state news agency RIA reported that some residents of a building in a southern Moscow street were evacuated.
— Natasha Turak
Kyiv endures third Russian attack in 24 hours, at least one dead
Ukrainian capital Kyiv faced a series of intense bombardments by Russia, including a rare daytime assault, totaling three separate attacks by drones and missiles in the span of 24 hours.
At least one person is dead after a fire caused by falling debris from an intercepted drone, Kyiv authorities said.
The Russian strikes sent people running for shelter. Ukrainian First Lady Olena Zelenska posted a video on her Twitter account showing children screaming and running for cover amid the sound of explosions.
The latest round of attacks began on May 28, which is Kyiv Day, marking the anniversary of the city's official founding. Sunday's bombardment lasted five hours and Ukrainian officials say 52 of 54 lethal drones launched by Russia were shot down by air defenses.
— Natasha Turak
Zelenskyy congratulates Erdogan on winning election
Ukrainian President Volodymyr Zelenskyy took to Twitter on Monday to congratulate Turkish President Recep Tayyip Erdogan on his win in Turkey's 2023 presidential election.
Erdogan's government has played a critical role during the ongoing war between Russia and Ukraine, specifically mediating the Black Sea grain deal, which unlocks Ukrainian produce exports blocked by Russia's invasion.
"In a phone call, I congratulated [President Erdogan] on winning the elections," Zelenskyy wrote on Twitter. "I noted the personal role of President in continuing the grain initiative, which is an important component of global food security. The cooperation between and is important and effectively contributes to the prosperity of our peoples and international stability. We will continue its further development and joint work to strengthen the security of the region, Europe and the world!"
Russian President Vladimir Putin also congratulated Erdogan, who is now entering his third decade in power, earlier in the day.
-- Gili Malinsky
Belarus' Lukashenko says there can be 'nuclear weapons for everyone'
Belarusian President Alexander Lukashenko said that if any other country wanted to join a Russia-Belarus union there could be "nuclear weapons for everyone".
Russia moved ahead last week with a plan to deploy tactical nuclear weapons in Belarus, in the Kremlin's first deployment of such warheads outside Russia since the 1991 fall of the Soviet Union, spurring concerns in the West.
In an interview on Russia's state television late on Sunday, Lukashenko, President Vladimir Putin's staunchest ally among Russia's neighbors, said that it must be "strategically understood" that Minsk and Moscow have a unique chance to unite.
He added that it was his own view - not the view of Russia.
Russia and Belarus are formally part of a Union State, a borderless union and alliance between the two former Soviet republics.
-- Reuters
Read CNBC's previous live coverage here:
Russia ramps up Kyiv bombardment; Putin and Zelenskyy congratulate Erdogan on reelection
