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 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 15-member crew, including seven Turkish nationals, seven Indian citizens and an intern from Libya, Russian news agency Tass quoted maritime authority as saying.

At least 11 sailors have died, Russian Maritime Agency was quoted by RT news, a Russian television network, as saying.

The agency did not specify the nationalities of persons killed in the accident.

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

Some three dozen sailors managed to escape the burning ships by jumping off the vessels.

Twelve persons have so far been rescued. Nine sailors are still listed as missing, the spokesperson said, adding that there were no chances to find survivors in the fire, the spokesperson said.

'As of 6am, the status of the operation has been reclassified to search from rescue because there is no hope to find survivors,' the spokesperson said.

The fire has not been extinguished. 'The blaze is ongoing,' he 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.

It's also the closest point of access for Russia to Crimea, a peninsula Moscow annexed in 2014. A Russian-built bridge over the Kerch Strait opened in May last year.

India is in touch with Russian authorities, officials said on Tuesday. 'We have been informed that two ships caught fire while moving through the Kerch Strait after one of them was apparently rocked by an explosion on 21 January,' external affairs ministry spokesperson Raveesh Kumar said.