Ukraine attempted Vladimir Putin's assassination, 2 drones shot down, claims Russia

Russia said it reserved the right to retaliate - a comment that suggested that Moscow might use the alleged incident to justify a further escalation in the 14-month-old war with Ukraine, said media reports.

Putin was not injured as he was not present on the premises when the alleged attack took place and there was no material damage to the Kremlin building.

Russia, meanwhile, considered the alleged drone attack "a planned terrorist act and an attempt on the life of the President of the Russian Federation."

"Two unmanned vehicles were aimed at the Kremlin... the devices were put out of action," the Kremlin said in a statement available to the media.

Ukraine has denied any role in the alleged attack and said it has "nothing to do" with it.

"Ukraine has nothing to do with drone attacks on the Kremlin," presidential spokesman Mikhaylo Podolyak said.

"Ukraine does not attack the Kremlin because, firstly, that does not solve any military aims," he added.

An unverified video circulating on Russian social media including the channel of the military news outlet Zvezda showed pale smoke rising behind the main Kremlin Palace in the walled citadel after the purported incident.

In a statement, Mayor Sergei Sobyanin said drone flights would be prohibited unless a special permit had been obtained from "government authorities".

He added that the ban was meant to prevent unauthorised drone flights that could "obstruct the work of law enforcement".

Following the alleged attack, the Kremlin said that the May 9 Victory Day parade would go ahead in Moscow as planned, the state-run TASS news agency reported.

Victory Day is a key anniversary for Putin, who often evokes the spirit and sacrifice that helped the Soviet Union repel Hitler's Nazis at a cost of some 27 million lives to boost patriotic sentiment.