Two Tanzania-flagged cargo vessels are ablaze in the Black Sea near the Kerch Strait, and Russian rescuers are trying to reach sailors who jumped overboard.
So far three have been rescued and one dead body has been recovered, Russia’s maritime agency Rosmorrechflot says.
One ship is a gas tanker, and the fire reportedly followed an explosion, which set the other vessel on fire.
They were named as the Kandy, with a crew of 17 from Turkey and India, and Maestro, with 14 sailors.
The Kerch Strait is a focus of tension between Russia and Ukraine.
In November Russian border guards seized three Ukrainian naval vessels near the narrow channel, which links the Black Sea with the Sea of Azov.
A court in Russia has extended by three months the detention of 24 Ukrainian sailors captured in the incident. They are accused of illegally crossing into Russian territory.
Ukraine condemned the Russian move, denying that its ships had violated the navigation laws in the area. The strait lies off Ukraine’s Crimea peninsula, which Russia annexed in 2014.