Russian President Vladimir Putin speaks to a Russian regional governor during a videoconference at the Kremlin, in Moscow, Russia, May 2, 2023. MIKHAIL KLIMENTYEV/AP

Russian authorities accused Ukraine on Wednesday of attempting to attack the Kremlin with two drones overnight. The Kremlin decried the alleged attack attempt as a "terrorist act" and said Russian military and security forces disabled the drones before they could strike.

In a statement carried by Russian state-run news agencies, it said there were no casualties. The Kremlin added that President Vladimir Putin was safe and continued to work with his schedule unchanged.

U.S. officials told CBS News on Wednesday that they were unable to immediately confirm any attempted drone attack on the Kremlin.

President Volodymyr Zelenskyy, visiting Finland on Wednesday, firmly denied any role in the alleged attack.

"We don't attack Putin or Moscow. We fight on our territory. We're defending our villages and cities," he said.

Ukraine presidential adviser Mykhailo Podolyak said the claims could be used by Russia as a pretext "to justify massive strikes on Ukrainian cities, on the civilian population, on infrastructure facilities" in the days ahead.

The Kremlin didn't present any evidence of the reported incident, and its statement included few details. Unverified videos posted on social media overnight purported to show at least one drone being shot down over the Kremlin, but the Kremlin did not reference the images.

Tass quoted the statement as saying that the Kremlin considered the development to be a deliberate attempt on Putin's life ahead of the Victory Day that Russia celebrates on May 9. Russia retains the right to respond "when and where it sees fit," the Tass report said, quoting the statement.

Russian officials have warned about potential drone strikes inside the country for weeks, as the country prepares to hold its Victory Day parade. A few hours before the Kremlin issued its statement about the alleged assassination attempt, Moscow Mayor Sergei Sobyanin said all drone flights over the city would be banned from Wednesday, with an exception for government devices.

Regions in the west of the country, close to Ukraine, have cancelled most public events, to not "provoke the enemy," as Belgorod governor Vyacheslav Gladkov recently put it in a live broadcast on social media.

The alleged incident on Wednesday came as Russia's security service claimed to have arrested members of a Ukrainian sabotage network planning attacks in Ukraine's Russian-occupied Crimean Peninsula. As CBS News senior foreign correspondent Charlie D'Agata reported from Dnipro, Ukraine, the claim from Moscow also came as another Russian oil depot burned.

An oil depot was damaged last month in a suspected Ukrainian drone attack, but that was in Crimea. This time, the fire erupted at a depot on the Russian side of the bridge connecting Crimea with Russia — firmly inside Russian territory — after apparently being hit by a Ukrainian drone.

D'Agata said the incidents appeared to be evidence of a significant escalation ahead of a long-anticipated Ukrainian counteroffensive on the battlefields of eastern Ukraine.

Attacks on Russian soil have been rare, but the frequency has increased in recent days.

There have been two freight train derailments in Russia this week. Moscow blamed at least one of them on an explosive device planted on the tracks.

In a rare move, Ukraine actually took responsibility for the previous oil depot attack, in Crimea, saying it was crucial to target Russia's logistical capacity ahead of the counteroffensive.

Regardless of any Ukrainian culpability in an attempted drone attack on the Kremlin Wednesday, if there was one, Russia was likely to press its claim as a pretext to escalate its own war against the neighboring country.

Vyacheslav Volodin, speaker of the Russian Parliament, said in a message posted on the Telegram messaging app Wednesday that Ukraine's, "Nazi regime must be recognized as a terrorist organization," accusing Ukrainian President Volodymyr Zelenskyy of "giving orders to carry out terrorist attacks."

"There can be no negotiations with the Zelenskyy regime" insisted Volodin. "We will demand the use of weapons capable of stopping and destroying the Kyiv terrorist regime."