Investigators inspect a building after a drone attacked the apartment in Moscow on Tuesday Photo: AP

The White House, meanwhile, said on Tuesday it did not support attacks inside Russia, and that it is still gathering information on the incident.

“What are these attempts to hide behind the phrase they are ‘gathering information’?” Anatoly Antonov, Russia’s ambassador to the US, said in remarks published on the Telegram messaging channel.

“This is an encouragement for Ukrainian terrorists.”

Russia has long accused what it calls the “collective West” of staging a proxy war against Moscow by supporting Ukraine with military and financial aid.

President Vladimir Putin also cast the assault, which brought the 15-month war in Ukraine to the heart of Russia, as a “terrorist act”. Ukraine, on the other hand, has accused Russia of “terrorism” for its bombing of Ukrainian civilians, allegations Moscow denies.

A Ukrainian presidential aide denied Kyiv was directly involved in the drone attack on Moscow, but said Ukraine was enjoying watching events and forecast more to come.

The drone attack on Moscow exposed glaring breaches in its air defences and underlined the capital’s vulnerability, analysts said.

Mark Cancian, a senior adviser with the Center for Strategic and International Studies, noted part of the reason why drones could make it all the way to Moscow undetected was because Russian air defences are mostly focused on fending off more sophisticated weapons.

“They are oriented on missiles, ballistic missiles, regional missiles, aircraft, bombers, but not short-range drones, you know, which might be flying very low over the ground,” Cancian said. “The Russian air defence was just not designed to do this.”

The Russian military will likely move some of its air assets away from the front line to help protect Moscow, Cancian said, a move that would weaken Russian troops in the face of a Ukrainian counteroffensive.