CAPE TOWN - A South African ship embarked on Sunday on a hazardous mission to rescue more than 100 people aboard a vessel trapped in Antarctic ice.

Organiser Gerald Hagemann told reporters before the ship's departure that despite the extreme cold and winter darkness, he hoped that the research vessel Agulhas, helped by an Argentine icebreaker, would be able to able to free the trapped ship.

"Based on present ice conditions we're very positive we will be able to reach the ship and bring it back...but that may change," he said.

"The biggest danger will be navigating through the icefield - there are only four hours of daylight now and much of the navigation will have to be done at night," he said.

Seventy-nine Russian scientists and 28 crew were aboard the German-owned Magdalena Oldendorff, which took refuge in a fjord after running into an impassable 40-50 mile (64-80 km) wide icebelt in the Antarctic. The vessel was stuck some 250 to 375 miles northeast of South Africa's Antartic research base.

Rescuers rushed to depart before worsening weather in the Antarctic winter makes the 2,580-mile (4,152-km) expedition from Cape Town impossible and the people on board the trapped ship run out of food and fuel - which is likely to happen in about three weeks.

"They're cold, but they know that help is on the way and they've got enough food for another month, so they'll be fine, said Hagemann, director of the Cape Town-based Antarctic Logistics Centre International.

MISSION WILL TRY TO FREE SHIP

Hagemann said that it would probably take about a week before the Agulhas meets the icebreaker Almirante Irizae on the edge of the pack ice, which is about 250 nautical miles from the trapped vessel.

If the rescue mission was unable to free the Magdelena Oldendorff, two military Oryx helicopters carried by the Agulhas would try to ferry most of its passengers to safety, leaving a skeleton staff with extra supplies for the rest of the winter.

But military experts say that temperatures of -50 degrees Celsius (-58.00 Fahrenheit), ice storms, and darkness would make this operation very dangerous. If the weather was too severe, helicopters would not be used, Hagemann said.

The Russian scientists on board the Magdalena Oldendorff had completed their research at the inland Antarctic research base and were on their way home when the ship, which had delivered supplies to their base, ran into pack ice on June 11.

Organisers say the entire rescue operation would probably cost about $2 million but it was not yet clear who would foot the bill. The trapped ship is owned by the Luebeck-based Oldendorff Carriers.

The Agulhas is owned by South Africa's Department of Environment and Tourism. It has a reinforced hull but cannot break a path through pack ice.