A Saturday morning attack, allegedly by Ukrainian-guided drones, has leveled two oil storage tanks near the Black Sea port of Sevastopol and damaged two neighbouring tanks at a storage depot, according to the latest pictures posted on social media by the city’s Russian-installed mayor Mikhail Razvozhayev.

Authorities in Kyiv have not acknowledged whether Ukraine is responsible for the attack, which came as many in Ukraine and the West believe Ukraine is preparing for a major offensive to retake Russian-occupied territories.

A major oil and products storage depot in the Gagarinsky district at Sevastopol was hit early in the morning on Saturday by two or three unidentified drones, igniting a major fire.

Razvozhayev said firefighters had fully extinguished the blaze by 3 p.m. No casualities have been reported, he said.

Drone pictures, which he posted at midday after the fire had been contained, suggest the full destruction of two storage tanks, with some damage inflicted to two similar tanks to the left and right sides.

The depot is the largest oil and products supply installation near the port of Sevastopol with a total of 23 storage tanks, according to Google Maps satellite images.

Sevastopol is a Russian chief military naval base for its Black Sea fleet and is a home to several carriers of cruise missiles, which Moscow has repeatedly used since October to attack Ukraine’s energy infrastructure.

About 150 firefighters have worked on the accident site, according to Razvozhayev’s online posts.

The oil depot was attacked by “two enemy drones” and four tanks burned, Razvozhayev said. A third drone was shot down over Crimea, and one more was deactivated through radio-electronic means, Moscow-appointed governor Sergei Aksyonov said, according to US news agency AP.

However, Razvozhayev later posted a correction, saying that just two drones participated in the attack, with one hitting a tank and the other shot down near the depot by Russian defence.

Moscow-based state news agency RIA Novosti quoted local residents as saying they had heard shots being fired and then two explosions at the oil depot, located on the shore of the Kazachaya Bay and about two kilometres from a military airfield.

Retail sales of fuels to the population will not be affected by the blaze, Razvozhayev said.

If Ukraine is to launch an offensive to reclaim Russian-occupied territories in the months ahead, drone and missile attacks deep behind the frontline to disrupt Russian supplies are seen as a precursor for its success, according to military analysts and observers.

Retaking the Crimea Peninsula is a prime goal of the expected Ukrainian offensive, ex-US General Ben Hodges told Newsweek.