The crew of a cargo ship captured by Somali pirates pounced on their sleeping captors today, disarming them and killing five before regaining control of their vessel which had been hijacked almost three months earlier, officials said.

A sixth pirate survived the attack by the crew of the Libyan-owned MV Rim and was taken hostage, said Abdiaziz Aw Yusuf, the district commissioner in Garacad, the Somalian coastal town near which the ship had been anchored.

A crew member was seriously injured during the struggle, the European Union's anti-piracy naval force said in a statement.

EU force commander Rear Admiral Jan Thornqvist sent the closest warship, the SPS Victoria, to provide medical assistance. A group of pirates on another hijacked vessel tried to block the warship, the statement said, but when the warship's helicopter approached the pirates, they fled.

The MV Rim was seized on February 3 in the Gulf of Aden, outside the internationally recommended transit corridor patrolled by the anti-piracy naval coalition.

The 4,800-ton ship is owned by White Sea Shipping of Libya and is carrying unknown cargo. The number and nationalities of its crew are also not known.

Somali pirates are currently holding at least 20 vessels.

The Horn of Africa nation's 19 years of lawlessness has allowed piracy to flourish, with attackers taking multimillion-pound ransoms for ships and crew.