Ukrainian helicopters breached Russian territory early Friday morning and bombed an oil depot in Belgorod, according to a Russian official.

“I can neither confirm nor reject the claim that Ukraine was involved in this simply because I do not possess all the military information,” said Ukrainian Foreign Minister Dmytro Kuleba.

CBS New reports:

A U.S. official confirmed to CBS News senior national security correspondent David Martin that Ukrainian helicopters did carry out the strike, and anther one a couple days earlier against an ammunition depot in the same area. The official told Martin there was concern in Washington about how Russia might react to the strikes.

The incident was the first airstrike on Russian territory since the invasion of Ukraine began in late February. The New York Times reports:

The strike appeared to be an embarrassment to Russia’s military, which said last week that Ukraine’s air force had been “practically destroyed.” Ukraine’s military had previously only managed to hit Russian territory with ground-launched missiles.

Belgorod, which has a population of about 400,000, sits less than 20 miles from the Ukrainian border. The region has been a staging ground in recent weeks for Russian troops entering eastern Ukraine.

The Times adds:

Video posted to VKontakte and verified by The New York Times shows two helicopters firing at the oil depot on the eastern edge of the city. Although it was not possible to determine whether the helicopters were Ukrainian, the footage confirmed that an airstrike caused a fire at the site. Other video of the aftermath shows the facility continuing to burn into the daylight.

Vyacheslav Gladkov, a regional governor in the Belgorod area, said two firefighters were injured trying to contain the blaze and that parts of the city were evacuated.

Kremlin spokesman Dmitry Peskov told reporters that the strike undermines peace talks, a stunning moment of hypocrisy from a man representing a military that has targeted civilians and broke promises to scale back operations in northern Ukraine.