Police Special Task Force troopers opened fire on Liberation Tigers of Tamil Eelam (LTTE) guerrillas who attacked a remote police post in the east, killing 15 rebel fighters, while the Navy killed two rebels wearing cyanide capsules around their necks as they tried to land by boat on the northern army-held Jaffna peninsula, officials said.

"The Navy killed two Sea Tigers as they were trying to infiltrate islands near Jaffna and damaged their boat. Frogmen are searching the sea to see if there are any more bodies," a military spokesman said.

In a separate incident, three policemen were killed when suspected Tigers detonated a Claymore fragmentation mine in the north central district of Vavuniya.

The LTTE was not immediately available for comment on the incidents.

The clashes came a day after suspected rebels fired mortar bombs at an army camp further north in the eastern district of Batticaloa, killing three soldiers and a civilian.

Also on Friday, the bodies of three slain Tamil men, one of them decapitated, were found by the roadside in the east.

The military said the trio were Tamil Tiger fighters who were abducted and killed by the rebels as they sought to defect. Pro-rebel Web site www.tamilnet.com said the three men had been abducted in Colombo by suspected paramilitaries aligned to the government in a white van and murdered.

White-van abductions are infamous in Sri Lanka. There have been dozens of reported cases in recent months in a new chapter in a two-decade civil war that has killed more than 65,000 people since 1983. Many residents accuse the military of being responsible.