Russian icebreakers on Wednesday managed to free two of five ships trapped in ice floes in the Sea of Okhotsk in the country's far east with more than 500 people on board.

The Admiral Makarov icebreaker, one of Russia's largest, rescued one fishing ship while a second ship managed to free itself from the ice, Russian television reported.

But a smaller icebreaker sent to carry out the rescue operation itself became trapped in the ice for several hours on Wednesday, Russian television reported, citing the transport ministry.

The federal fishing agency said later Wednesday that the Admiral Makarov had managed to lead the smaller icebreaker into a clear area.

The remaining ships -- a fish canning factory ship, a refrigerator ship and a fisheries research vessel with more than 400 passengers on board -- have been trapped since December 30.

"Their position is stable. There is no danger," the Admiral Makarov's captain Gennady Antokhin told Russian television.

The icebreaker was due to reach the remaining three ships by midnight local time (1400 GMT), Russian television reported.

"The ice is very serious, frozen in layers, covered in snow and hard to pass through. It sticks onto the ship," the captain of the Admiral Makarov, Antokhin, told Channel One television.

"I think this will not be a very quick operation," he added, speaking via telephone.

Prime Minister Vladimir Putin on Tuesday talked to the captain of one of the ships by telephone, telling him to "hold on."

He also met the transport minister Igor Levitin to discuss the situation. Levitin said the situation was exacerbated by difficult weather conditions, with winds blowing up to 30 metres per second.

In late December 10 ships were initially trapped by ice in the Sakhalin Gulf in the south-west of the Sea of Okhotsk, but seven managed to escape.

A further two ships later became trapped this week, despite weather warnings. It was these ships, with more than 100 people aboard, that were freed Wednesday.