Nairobi/Mogadishu - Pirates have hijacked a Malaysian tanker with over 20 crew members on board in the Gulf of Aden, the International Maritime Bureau's piracy reporting centre said Wednesday.

The body said that the ship, which is carrying crude palm oil, is thought to be heading into Somali coast waters.

A ransom demand is expected to be issued soon.

Piracy off Somalia's lawless coast has surged in the last three months. Prior to the latest attack, the IMB said that eight vessels had been attacked in the region and issued a fresh warning for the Gulf of Aden.

A general cargo ship was hijacked on August 12, and is currently being held for ransom along with its 28 crew, the IMB said.

Two German citizens seized from their yacht in late June were recently released after a ransom of one million dollars was paid.

Somalia's weak transitional government, currently engaged in countering a bloody insurgency, is powerless to stop the pirates from seizing ships and cashing in.

"The situation in this region is grave," IMB Director Pottengal Mukundan said in a statement. "These pirates are not afraid to use significant firepower in attempts to bring vessels under their control."

Pirates, armed with rocket-propelled grenades and automatic weapons, use speedboats to pursue their targets.

The United Nations Security Council has approved incursions into Somali waters to fight piracy, and the IMB said it understood that coalition warships had helped prevent two attacks.

However, Mukudan said that using coalition warships was "by no means a long-term solution."

"It is clear that the threat or presence of coalition navies has done little to stem the tide of attacks in this region," he said.

Somalia has been in a state of anarchy since the overthrow of dictator Mohamed Siad Barre in 1991. (dpa)