Eleven people were rescued when a Dutch cargo ship sank off the Belgian coast after colliding with a gas tanker sailing under the flag of the Marshall Islands yesterday.

The accident happened in the Northern Sea off the port of Zeebrugge in a very congested area that includes the ports of Rotterdam and Antwerp, Europe's two largest harbours.

Some 20 ships and volunteers from the search and rescue organization Vrijwillige Blankenbergse Zeereddingsdienst (VBZR) were involved in the rescue operations, Western Flanders Provincial governor Carl Decaluwe told local media.

He added the vessel, MV Flinterstar, carrying 3,000 tonnes of steel and iron and 140 tonnes crane parts, is now laying at a depth of 130 metres underwater.

The ship owner, Flinter, issued a statement on its website saying the 9000-tonne vessel had been stabilised, adding that salvage companies and its insurers had been contacted to discuss how the vessel would be salvaged.

Belgian media reported that two people were taken to hospital, including the captain of the ship who suffered hypothermia, and was soaked in oil.

It also reported that the other vessel, gas tanker Al-Oraiq was slightly damaged during the collision and was brought to Zeebrugge.

The ship had 73 tonnes heavy-fuel and 125 tonnes of diesel oil on board. Two large oil stains were detected. One is three kilometres long and two kilometres wide, the other is three kilometres long and 100 metres wide.