US think tank the Institute for the Study of War says an alleged drone attack on Russia's presidential office was likely staged by the administration of President Vladimir Putin.

The Kremlin said in a statement on Wednesday that two unmanned aerial vehicles targeted the presidential office in Moscow.

The statement accuses the Ukrainian administration led by President Volodymyr Zelenskyy of carrying out the strike.

It calls the incident a pre-planned act of terrorism by the Zelenskyy administration to assassinate President Putin, and threatens retaliation.

Russian media say the drone strike took place at around 2 a.m. on Wednesday local time, and that the federal investigative committee launched a probe.

Zelenskyy has strongly denied Ukraine's involvement. He said that Putin is looking for a way to motivate his people.

US Secretary of State Antony Blinken said that he has seen the reports, and that he can't in any way validate them.

He added, "I would take anything out of the Kremlin with a very large shaker of salt." He said that the US government will determine what the facts are.

The think tank noted in its assessment on Wednesday that "Russian authorities have recently taken steps to increase Russian domestic air defense capabilities, including within Moscow itself."

The institute said that "it is therefore extremely unlikely that two drones could have penetrated multiple layers of air defense and detonated or been shot down just over the heart of the Kremlin."

It said that Russia likely staged the drone strike in an attempt to "set conditions for a wider societal mobilization."

The alleged attack comes ahead of a Victory Day Parade in the Russian capital on Tuesday.

The institute said that "The Kremlin may use the strike to justify either cancelling or further limiting May 9th celebrations."