On Thursday Somali pirates hijacked a tanker and its crew of 12 Filipinos and one Indonesian in the Gulf of Aden, a diplomat said.

The diplomat, who is based in Nairobi, asked that his name not be used because he is not authorized to speak to the media. It was not immediately clear what cargo the tanker was carrying.

Piracy has taken an increasing toll on international shipping, especially in the Gulf of Aden, one of the world's busiest shipping lanes. Pirates made an estimated $30m hijacking ships for ransom last year, seizing more than 40 vessels off Somalia's 3 000km coastline.

Somali waters are now patrolled by more than a dozen warships from countries including Britain, France, Germany, Iran and the United States.

China and South Korea have also ordered the dispatch of warships to protect their vessels and crews from pirates.

Somalia, a nation of about eight million people, has not had a functioning government since warlords overthrew a dictator in 1991 and then turned on each other.

Its lawless coastline is a haven for pirates.