A major explosion occurred on Friday in Taganrog, a southwest Russian port on the Sea of Azov, injuring at least 12 people, emergency services have told the TASS news agency.
The blast, in the city center, sent a large column of dust into the air, footage circulating online shows.
Several nearby buildings have been damaged, with their windows shattered and a number of people are feared to be trapped under debris.
The governor of Rostov Region, where Taganrog is located, said a preliminary assessment shows the explosion was caused by a missile strike. Vasily Golubev added that emergency crews are working at the scene, and no fatalities have been reported.