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A Russian ice-breaker is labouring through howling winds and heavy snow as it tries to reach ice-bound ships in the Sea of Okhotsk where more than 500 sailors are trapped.

Three of the vessels have been trapped since Friday in ice estimated at two metres thick.

RIA Novosti, Russia's state-owned news agency, said two more ships became stuck on Monday.

"At this point with the arrival of the ice-breaker, I think that it will try to tow the Cape of Elizaveta and the Anton Gurin after it," Vyacheslav Nagonyuk, director of the Special Fleet Department at the Far East Shipping Company (FESCO), said.

The Sea of Okhotsk is an arm of the northern Pacific to the west of Russia's Kamchatka Peninsula.

The ice-breakers were on Tuesday concentrating on a trawler seen as being in the most danger because it is drifting and only about one kilometre from land, Russian news reports said.

A statement from the Russian transport ministry said there was no immediate danger to the crews, who have sufficient food and water.

The ministry said an ice-breaker was expected to reach their vicinity early on Thursday.

Nikolay Shatalin, hydrologist engineer of the Special Fleet Department at FESCO, gave warning that the weather is likely to get worse, which would complicate the rescue operation.

"On 4th and 5th of January we'll have a break in heavy wind, but after that the Sea of Okhotsk will see another cyclone and it will mean a storm, a heavy gale and poor visibility," Shatalin said.

Source: Al Jazeera and agencies