Suspected Tamil Tigers blew up their fishing boat Saturday to avoid capture by a navy patrol off the west coast of Sri Lanka, leaving six rebels dead and eight sailors missing, the military said.

The incident was the most serious since government and rebel negotiators met in Geneva last month to try to salvage a four-year-old cease-fire.

Tamil Tiger rebels said they had nothing to do with the blast.

"We have no involvement at all," Seevaratnam Puleedevan, a top rebel leader, told The Associated Press by phone from the Tiger stronghold of Kilinochchi.

"There are a lot of smuggling and illegal activities going on in that area, including illegal immigration. It could be one of those boats involved," Puleedevan said. "We have checked with the Sea Tigers' western command. They have confirmed that they are not involved."

The Norwegian-led Sri Lanka Monitoring Mission said Sunday it was too early to assign blame for the attack.

"We are currently conducting inquiries. The LTTE has denied any involvement, however, based on mission's previous experience during the period of cease-fire, we feel that we can not at this stage rule out LTTE's involvement," mission spokeswoman Helen Olafsdottir said in a statement, using the initials of the rebels' official name.

A navy boat spotted the fishing vessel near Kalpitiya and, suspecting it was being used to smuggle explosives, began to chase it, military spokesman Brig. Sudhir Samarasinghe said.

The suspected rebels then blew up their vessel, damaging the approaching navy boat, Samarasinghe said. The fishing boat was destroyed in the blast killing all six aboard, he said.

Eleven sailors on the navy boat were rescued but eight were still missing, he said.

Kalpitiya is a fishing area some 90 miles north of the capital, Colombo.

Tamil Tiger rebels have been battling the government since 1983 to create a separate state for ethnic minority Tamils, alleging discrimination by the majority Sinhalese. More than 65,000 people died in the conflict before a Norwegian-brokered cease-fire was signed in 2002.

The truce has become increasingly shaky recently, with more than 160 people, including 81 government security personnel, killed since December.

In Geneva, both sides agreed to scale down violence and meet again on April 19-20.

In a similar incident on Feb. 11, suspected guerrillas blew up their boat off Sri Lanka's northwestern coast, killing all four rebels on board and injuring a sailor whose naval boat had approached them.