Originally Published: 03 MAY 23 09:50 ET

Updated: 03 MAY 23 13:43 ET

By Sebastian Shukla and Nathan Hodge, CNN

(CNN) -- Russia claimed Ukraine launched an attempt to kill Russian President Vladimir Putin with a drone strike on the Kremlin overnight on Wednesday, an extraordinary allegation that was met with forceful denials in Kyiv.

The Kremlin said the attack was foiled and the alleged drones destroyed. Video that appeared on social media shows a bright flash and a puff of smoke over a part of the Kremlin, the official residence of the Russian president and the most potent symbol of power in Moscow.

In a statement, the Kremlin said it regarded the alleged attack as terrorism and a deliberate attempt on Putin's life. "Russia reserves the right to take retaliatory measures where and when it sees fit," it added.

Ukraine denied involvement in the alleged strike. "As President Zelensky has stated numerous times before, Ukraine uses all means at its disposal to free its own territory, not to attack others," the Ukrainian presidential spokesman, Sergiy Nykyforov, told CNN on Wednesday.

US officials said they were still assessing the incident, and had no information about who might have been responsible. Whatever the truth, any admission of a security breach at the heart of the Kremlin is remarkable.

Moscow said the alleged attack took place in the early hours of Wednesday. The Russian president was not in the building at the time, Kremlin spokesperson Dmitry Peskov said.

CNN analysis of video showing the incident support the Kremlin's claim that two drones were flown above the Kremlin early Wednesday, but did not show evidence of Ukrainian involvement:

A video that appeared to show smoke rising from the Kremlin surfaced on a local neighborhood channel on social media platform Telegram at 2:37 a.m. local time Wednesday. The first reports of the incident citing the Kremlin came via Russian state media TASS and RIA around 2.33 pm local time -- around 12 hours later.

Shortly after the first media reports, another video appearing to show the moment a drone exploded above the Kremlin began circulating widely on social media. In the video, the drone appears to fly towards the building's domed roof, followed by what looks like a small explosion.

In this video, two people appear to be climbing on the dome holding flashlights, and can be seen ducking down just before the moment of the explosion. The people climbing the drone are not present in the first of these videos, but appear in the second, suggesting they were responding to the fire caused by the first drone at the time the subsequent drone appeared.

An 'attempt on the President's life'

The Kremlin Press Service has called the purported drone attack an "attempt on the President's life," said it was an "act of terrorism" and blamed Ukraine.

But Kyiv said that accusation of terrorism was better directed at Russia. "A terror attack destroyed blocks of residential buildings in Dnipro and Uman, or a missile at a line at Kramatorsk rail station and many other tragedies," said Nykyforov, the Ukrainian presidential spokesman.

"What happened in Moscow is obviously about escalating the mood on the eve of May 9." That day is known as "Victory Day" inside Russia, commemorating the Soviet Union's role in defeating Nazi Germany in World War II.

"It's a trick to be expected from our opponents," he said.

Ukrainian presidential adviser Mykhailo Podolyak also denied Kyiv had any involvement and said it made no sense for Ukraine to have carried out the alleged strike.

"First of all, it absolutely does not solve any military goals. And it is very unhelpful in the context of preparing for our offensive actions. And it definitely does not change anything at a battlefield," he said. "This would allow Russia to justify mass strikes on Ukrainian cities, civilians and infrastructure facilities. Why would we need that? What's the logic?"

Podolyak also said Moscow's claims were an attempt at controlling the narrative ahead of a much-anticipated Ukrainian counteroffensive.

"Russia without a doubt is very afraid of Ukraine starting an offensive on the front line and is trying to seize the initiative, distract the attention and create distractions of a catastrophic nature," he said. "So, Russian statements on such staged operations need to be taken as an attempt to create pretext for a large-scale terrorist attack in Ukraine."

A US official said Washington had no warning about the alleged drone attack. "Whatever happened, there was no advanced warning," the official told CNN, adding that authorities are still trying to find out more.

Another US official told CNN they are still working to assess Russia's claims, and have not yet validated the Kremlin assertion that Ukraine tried to assassinate Putin.

US Secretary of State Antony Blinken said he had seen reports from Moscow about the alleged attack, but "can't in any way validate them."

"We simply don't know," Blinken said Wednesday at a Washington Post Live event.

"We'll see what the facts are. And it's really hard to comment or speculate on this without really knowing what the facts are," Blinken added.

The founder and financier of the Wagner private military company, Yevgeny Prigozhin, declined to comment on the alleged attack when asked about the incident.

"I can't comment on this phenomenon in any way. Maybe it was lightning," Prigozhin said in a post on his official telegram channel. Instead, the Wagner leader asked for more ammunition.

In his response to the attack, Russian State Duma Speaker Vyacheslav Volodin called for the use of weapons capable of "stopping and destroying the Kyiv terrorist regime."

Kyiv is approximately 862 kilometers (about 535 miles) from Moscow. Russia has accused Ukraine of multiple attempted drone strikes deep inside Russian territory, including one earlier this year when the governor of the Moscow region claimed a Ukrainian drone had crashed near the village of Gubastovo, southeast of the capital.