The Semlow, freed last week, was taking aid for victims of the tsunami

The MV Torgelow with a crew of 10 was seized by gunmen near the port of El-Maan, 40km from Mogadishu.

The hijacking comes a week after another ship was freed after being held captive for nearly three months.

The International Maritime Bureau says there have been at least 20 attacks on ships in Somali waters since March.

Kenya's Assistant Immigration Assistant Minister Ananiah Mwaboza told KBC radio that the government might cut ties with the Somali government if any of the warlords participating in the government are linked to the gunmen who hijacked the ship.

Charter

The MV Torgelow was a privately chartered ship carrying tea, oil and also fuel for the MV Semlow, its sister ship released last week.

The Semlow had been carrying UN food aid to Somalia when it was overpowered by gunmen. The capture of the MV Torgelow is the latest in a series of attacks on vessels entering Somali waters.

Captain Pottengal Mukundan of the International Maritime Bureau said the recent hijackings made Somali waters some of the most dangerous in the world, and there were strong suspicions that Somali warlords were behind the attacks.

"There is no local government infrastructure, no law enforcement or judicial authorities in Somalia," Capt Mukundan said.

"Areas are controlled by the warlords. So pirates can do what they want and get away with it. And we think that some of these warlords may be involved."

Volunteers

Karim Kudrati of the Kenya-based Motaku Shipping Agency said the Sri Lankan captain and the nine Kenyan crew members had volunteered to make the trip.

Somalia's dangerous waters

"I am surprised these people are doing this and especially in the holy month of Ramadan. I think we have to withdraw from this service," he told Kenyan television.

The MV Semlow was finally released last week in a deal brokered between the pirates and a Somali businessman with its rice cargo - intended for Somali victims of the Indian Ocean tsunami - intact.

It had run out of fuel and was waiting in El-Maan for supplies before returning to Mombasa in Kenya.

Authorities at the port said the pirates were not paid and had released the Semlow unconditionally.