Russian helicopters battled freezing conditions on Saturday to rescue the scientists from a research base that was all but crushed beneath a wall of ice.

"The mission to save our people can be considered successful," Interfax reported mission chief Artur Chilingarov as saying. "[We have] on board our helicopter all 12 explorers and two dogs."

Rescuers flew for four hours before evacuating the researchers from the station in temperatures of minus 39C. They were due to arrive back on Norway's Spitzbergen islands in the evening.

The scientists were unharmed after their ordeal huddled in the remains of their base, cast 700km from the nearest land on a drifting ice floe, Russian state television reported.

Ice wall

The windswept outpost was almost completely destroyed when a 10m high ice wall reared up from the surrounding ice floe and collapsed on the base on Wednesday.

Authorities immediately launched a rescue mission, but progress was hampered by vast distances and freezing conditions around Europe's northern tip.

They were also hindered by difficulties in landing heavy helicopters on the sheet ice under the base.

"Such a long flight is a challenge in itself in areas where people haven't flown so much before," said Odd Olsen, the senior Norwegian official on Spitzbergen. "And there are few alternative landing spots."

Russia's first permanent research station near the North Pole since the fall of the Soviet Union enjoyed generous scientific funding. Severny Polyus-32 was seen as a symbol of the country's return to polar exploration.

The base had almost completed a full polar circle on drift ice since its launch in April last year.