Two ships carrying Indian, Turkish and Libyan crew members have caught fire in the Kerch Strait separating Crimea from Russia, killing at least 11 persons, media reports said on Tuesday.

The fire broke out on Monday off Russia’s territorial waters. Both vessels were flying Tanzanian flags. One of them was a liquefied natural gas (LNG) carrier and another one was a tanker. The fire broke out as the two ships were transferring fuel from one to the other.

One of the ships, the Candy, had a 17-member crew, including nine Turkish citizens and eight Indian nationals.

The other one, the Maestro, had a 15-member crew, including seven Turkish nationals, seven Indian citizens and an intern from Libya, Russian news agency Tass quoted the maritime authority as saying.

At least 11 sailors have died, the Russian Maritime Agency said, according to a report by Russian television network RT news.

“Presumably, an explosion occurred (on one of the vessels). Then the fire spread to the other vessel. A rescue tug is en route,” said a spokesman for the Russian Maritime Agency.

Some sailors managed to escape the burning ships by jumping off the vessels. Twelve persons have been rescued from the sea so far. Nine sailors are still listed as missing, the spokesperson said.

Severe weather conditions at sea have prevented rescue ships from taking victims to the shore for medical treatment, the report added.

The Kerch Strait is a key waterway that holds strategic importance for both Russia and Ukraine. It is an important economic lifeline for Ukraine that allows ships leaving the port city of Mariupol to access the Black Sea.