Ukraine’s foreign minister, Dmytro Kuleba, said he could not confirm or deny reports of Ukrainian involvement in the strike as he did not have military information. The Ukrainian Defence Ministry and the general staff did not respond to requests for comment.

Video footage of the purported attack — the first accusation of a Ukrainian air strike on Russian soil since Moscow launched its invasion of Ukraine on Feb. 24 — showed what looked like several missiles being fired from low altitude, followed by an explosion. Reuters could not immediately verify the footage.

Regional governor Vyacheslav Gladkov said on messaging app Telegram that two Ukrainian helicopters struck the facility in Belgorod, some 35 kilometres (22 miles) from the border with Ukraine, after entering Russia at low altitude.

The resulting blaze injured two workers, Gladkov added, while some areas of the city were being evacuated.

However, Russian oil firm Rosneft ROSN.MM, which owns the fuel depot, said in a separate statement that no one was hurt in the fire. The company gave no information on the cause of the fire.

A witness told Reuters that another blast was heard in the city at around 1020 GMT. The cause of the blast was not immediately clear.

Speaking to reporters on a conference call, Kremlin spokesman Dmitry Peskov said President Vladimir Putin had been briefed about the incident. Peskov said the strike could jeopardise Moscow’s peace negotiations with Kyiv.

“Of course this cannot be perceived as creating comfortable conditions for continuing the talks,” Peskov said, adding that everything was being done to prevent disruptions in fuel supplies in the city.

In separate comments, Energy Minister Nikolai Shulginov said the incident would not affect the region’s fuel supplies or prices for consumers.

The governor of the neighbouring Kursk region, Roman Starovoit, said its own fuel supplies were sufficient to last several weeks and called on the population not to stockpile fuel.

An ammunition depot near Belgorod caught fire on Wednesday, causing a series of blasts. At the time, Gladkov said authorities were waiting for the Russian defence ministry to establish its cause.

Moscow calls its intervention in Ukraine “a special military operation”.

(Reporting by Olzhas AuyezovEditing by Bradley Perrett and Frances Kerry)