Two of the pirates were killed and five captured. Three of the ship's crew were injured, US military officials said.

The ship's capture was reported on Tuesday morning by the East African Seafarers' Assistance Programme.

Somalia is notorious for piracy. Only Indonesia's waters are considered more prone to pirate attacks.

Only on Monday, a Japanese vessel was seized off the East African coast.

Ransom demand

A helicopter was sent from the warship USS James E Williams to investigate reports of the MV Dai Hong Dan's hijacking, the US military said in a statement.

We are waiting for the ship to return to port, if nothing happens as they sail back, so that we can get more information

Andrew Mwangura

East African Seafarers' Assistance Programme

Navy officials ordered the pirates to surrender their weapons by radio, and the ship's 22 crew then managed to overpower the hijackers, the military said.

Andrew Mwangura, from the Seafarers' Assistance Programme, told AFP news agency the vessel had been was contracted by Mogadishu traders to deliver general cargo.

He said it was believed the ship's crew were from southern Asian nations.

"We are waiting for the ship to return to port, if nothing happens as they sail back, so that we can get more information," Mr Mwangura said.

After Tuesday's hijack, militiamen demanded a $15,000 (£7,250) ransom to free the vessel, said Paddy Ankunda, a spokesman for African Union troops in the Somali capital Mogadishu.

"The hijacking was masterminded by the same people who were supposed to bring it into the dock," he said.

The freighter had apparently unloaded its cargo - thought to have been sugar from India - by the time of its capture.

Mr Mwangura said the crew were sailing the ship back to Mogadishu after defeating the pirates.