The Kremlin said the reported Ukrainian air strike on Belgorod, a town around 40 kilometres (25 miles) from Russia's border with Ukraine, would hinder future peace talks.

"Of course, this is not something that can be perceived as creating comfortable conditions for the continuation of negotiations," Kremlin spokesman Dmitry Peskov told reporters.

Also on Friday, Russian and Ukrainian negotiators resumed peace talks via video conference, following face-to-face talks in Istanbul earlier this week.

Both Ukraine's foreign and defence ministries said they could neither confirm nor deny that Kyiv was behind the attack.

"I am a civilian," Ukrainian Foreign Minister Dmytro Kuleba told reporters in Warsaw.

Defence ministry spokesman Oleksandr Motuzyanyk said Ukraine should not "take responsibility for all miscalculations, all disasters and all events taking place on Russian soil".

The incident marked the first time Russia has reported a Ukrainian air strike on its territory since the conflict began.

Russia's announcement came on the 37th day of Russia's military campaign in Ukraine, with thousands killed and more than 10 million displaced in the worst refugee crisis in Europe since World War II.

- Petrol panic buying -

Moscow has repeatedly said it has destroyed Ukraine's airforce.

"There was a fire at the petrol depot because of an air strike carried out by two Ukrainian army helicopters, which entered Russian territory at a low altitude," Belgorod region governor Vyacheslav Gladkov wrote on messaging app Telegram.

Two employees at the storage facility were injured in the fire, he said.

Some 170 firefighters battled to put out the enormous blaze, which started around 6:00 am (0300 GMT), the emergencies ministry said.

A massive fire was raging, with black and white smoke billowing overhead, a video released by the ministry showed.

Russian energy giant Rosneft, which owns the facility, said it had evacuated staff.

Long lines of cars formed at filling stations, but the governor urged residents to refrain from panic buying, saying there was enough petrol.

"There aren't any problems with fuel in the region and there won't be any," Gladkov said.

Russian President Vladimir Putin has been notified of the strike, Peskov told reporters.

He insisted that it was "an absolute fact" that Russia had air supremacy in the conflict.

Earlier this week, explosions could be heard from an arms depot in Belgorod, but the authorities did not provide any clear explanation for the blasts.

Belgorod lies around 80 kilometres from the Ukrainian city of Kharkiv, which has been pummelled by Russian forces since Moscow sent troops to Ukraine on February 24.

Separately, the Russian defence ministry said that Moscow had destroyed six military facilities in Ukraine, including five depots containing ammunition, rockets and artillery weapons.

bur/ach

ROSNEFT