Two ships -- a Chinese icebreaker and a Russian research vessel -- broke free Tuesday from thick Antarctic ice where they had been trapped for days.

China's Xue Long, which became stuck after rescuing passengers from the Russian vessel, "pulled free of the ice and navigated into the open waters", the official Xinhua news agency reported from on board.

State broadcaster China Central Television said the Xue Long (Snow Dragon) spent 14 hours working to break through the ice and finally reached open waters at 6pm Beijing time (1000 GMT).

And the Russian vessel Akademik Shokalskiy, which had been trapped in frozen seas since Christmas Eve, was now moving slowly after a crack appeared in the ice, its captain Igor Kiselyov told Russia's ITAR-TASS news agency.

"Finally the wind changed to the west and as a result a crack appeared in the ice. We went into it and we are now slowly moving north," he said.

"We are going at a slow speed and by changing course, we have moved forward already more than 20 miles," Kiselyov added.

He acknowledged the sailing conditions were "hard", with thick fog and visibility of no more than 500 metres.

Nevertheless, the going was better than before, he said, with the ship moving through smaller chunks of ice.

A crew of 22 remained on the Akademik Shokalskiy after the 52 passengers including tourists, journalists and scientists were airlifted last Thursday by a helicopter from the Xue Long to the safety of an Australian vessel.

The 52, who spent Christmas and New Year stranded aboard the ship in Antarctica's Commonwealth Bay, were due to arrive at Australia's Casey research base Tuesday night, with a return to Australia expected in two weeks.

But the Chinese icebreaker itself became trapped after its mercy mission, until breaking free Tuesday.

A westerly wind had been expected to give it its best chance of escaping, according to the China Daily newspaper before the breakout.

The wind was expected to help push away some of the heavy ice surrounding the ship, according to Xinhua, which noted that the biggest floes were three times thicker than the Xue Long's ice-breaking capacity.

Chinese state media hailed the ship's rescue mission.

"Its performance, especially the success in rescuing all the passengers, has been given the thumbs up by global public opinion," the Global Times said. "China should be proud of it."

"Xue Long's mission is an epitome of China's attitude toward its international obligations," it added.

The Chinese ship has 101 people on board, while 22 crew remain on the Shokalskiy.

The ice surrounding the Xue Long was up to four metres (13 feet) thick, with the nearest open waters 21 kilometres (13 miles) away, Xinhua reported.

In recent days, it had prepared for a breakout by warming up its engine and creating a channel about one kilometre long and described as an "ice-breaking runway".

The Polar Star, a US Coast Guard icebreaker, had cut short a stop in Australia to go to the aid of both ships.

It had originally been expected to arrive on Sunday but it was unclear whether it would now turn back.