THE HAGUE, Netherlands -- A cargo ship sank Wednesday night after colliding with another vessel on the North Sea, and rescuers in helicopters and ships were plucking crew members from life rafts and searching for others, Dutch authorities said.

The 148-meter Baltic Ace collided with the 134-meter container ship Corvus J near busy shipping lanes some 65 kilometres off the coast of the southern Netherlands. The Baltic Ace had a crew of 24, some of whom were believed to be in the icy waters.

"We have found life rafts, and the people in them are being picked up by helicopters," coast guard spokesman Peter Verburg said.

By around 10 p.m. local time 11 crew members had been rescued by helicopters and two more by ships, the coast guard said in a statement. Rescuers were using infrared cameras to hunt for more survivors.

In a statement, the Dutch Defence Ministry said two navy patrol ships were aiding in the search. "Helicopters are trying, in (strong wind) and high waves to bring the people to safety," the ministry said.

Verburg said the 12-man crew of the Corvus J was still on board the ship, which was helping in the rescue operation. "It is badly damaged, but not in danger of sinking," he said of the Corvus J.

The coast guard spokesman said the cause of the collision was not known. "At the moment we are solely focused on getting the people to safety," he said.

Four of the survivors were being flown to a hospital in Rotterdam and seven to an airbase in Belgium.

The Baltic Ace was heading from the Belgian port of Zeebrugge to Kotka in Finland and the Corvus J was on its way from Grangemouth in Scotland to Antwerp, Belgium.