Ukraine carried out a missile strike on Friday on the headquarters of Russia’s Black Sea Fleet, a Russian official said, as large plumes of smoke were seen coming from Sevastopol harbour in the annexed Crimea.

The Russian-installed governor of Sevastopol, Mikhail Razvozhayev, warned Sevastopol residents that “another attack is possible” and urged them not to leave buildings. “Those who are near the fleet headquarters, head to the shelters if you hear the siren,” he said, adding that firefighters were battling a blaze at the site of the attack, and more emergency forces were being brought in, an indication that the fire could be massive.