Russia on Wednesday accused Ukraine of carrying out a drone attack on the Kremlin in a failed bid to kill President Vladimir Putin.

The Kremlin said two drones had been used in the alleged attack on Putin's residence in the Kremlin citadel, but had been disabled by electronic defenses.

Kremlin spokesperson Dmitry Peskov told Russia's state news agency RIA Novosti that Putin wasn't in the Kremlin at the time and was working from the Novo-Ogaryovo residence.

The Kremlin added that Putin was safe and his schedule was unchanged.

It also said Russia 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.

There was no immediate comment from Ukrainian authorities.

"Two unmanned aerial vehicles were aimed at the Kremlin. As a result of timely actions taken by the military and special services with the use of radar warfare systems, the devices were put out of action," the Kremlin said in a statement.

"We regard these actions as a planned terrorist act and an attempt on the president's life, carried out on the eve of Victory Day, the May 9 Parade, at which the presence of foreign guests is also planned ...

"The Russian side reserves the right to take retaliatory measures where and when it sees fit."

It said fragments of the drones had been scattered on the territory of the Kremlin but there were no casualties or material damage.

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 complex after the purported incident.