Video images of the purported attack posted online showed what looked like several missiles being fired from low altitude, followed by an explosion. Reuters has not yet been able to verify the images.

The helicopters struck the facility after crossing the border at low altitude, regional governor Vyacheslav Gladkov said on messaging app Telegram.

The resulting blaze injured two workers, Gladkov added, while some areas were being evacuated in the city near the Ukrainian border.

However, Russian oil firm Rosneft, which owns the fuel depot, said in a separate statement that no one was hurt in the fire, though it gave no information on the cause.

Ukraine’s defence ministry could not immediately be reached for comment.

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 action in Ukraine “a special military operation”.