Six sailors from the fast attack craft (FAC) were rescued by another boat patrolling the waters off the Tamil Tiger stronghold of Mullaitivu district, spokesman D. K. P. Dassanayake said.

'The officer in charge and five others from the FAC were rescued,' Mr Dassanayake said. 'One of them said the craft started taking in water after a huge explosion. They got into a life raft.'

The pro-rebel Tamilnet.com website reported that the Dvora-class fast attack craft was sunk in a suicide attack launched by the Liberation Tigers of Tamil Eelam (Ltte).

Three 'Black Sea Tigers,' or suicide bombers, perished in the attack, Tamilnet said quoting Tiger sources.

However, Mr Dassanayake denied there had been any confrontation with the Tigers and insisted that the navy vessel was sunk in a sea mine blast.

A search was underway for the other 10 crewmen after the pre-dawn blast, which occurred as attack craft were patrolling for suspected Tamil rebel activity.

Clashes between suspected Tamil Tiger ships and the Sri Lankan navy have escalated in recent months amid heavy fighting in the island's embattled northern and eastern regions.

In February, suspected Tamil Tiger rebels sank a navy speedboat near the maritime border with India, leaving five sailors missing.

Thousands of people have been killed in a new wave of fighting since December 2005 when a Norwegian-brokered truce began to unravel. The truce was formally ended by the government in January.

The Ltte relies on ships to transport black market weapons to the northern part of the island under their control. The rebels have been fighting for a separate Tamil state since 1972.

The military has pushed out the Ltte from their last bastion in the east of the tropical island, a victory that has largely confined the rebels to their northern mini-state. -- AFP