Colombo: Sri Lanka's military sank four Tamil Tiger rebel boats on Thursday off the island's northern coast after a battle that killed eight rebels and one soldier, while six civilians were killed in a rebel artillery attack, the military said.

A military official said the rebel boats were sunk when troops fired artillery at them as they attempted to attack army and naval positions in Sirutheevu off northern Jaffna. The remaining boats fled.

The battle left eight rebels and one soldier dead and two soldiers wounded, the official said, speaking on condition of anonymity citing government rules. He said one soldier and two sailors were missing.

Also on Thursday, air force helicopters and jets bombed a rebel gathering point in northern Mannar district and two camps in Mullaitivu district, the official said.

He said the raids were successful but did not give details of casualties or damage.

Meanwhile, six civilians were killed on Thursday in rebel artillery fire in Pashaiyur, Columbuthurai and Gurunagar villages on the Jaffna peninsula, the official said.

Rebel spokesman Rasiah Ilanthirayan could not immediately be reached for comment.

However, a pro-rebel Web site reported that the guerrillas raided a navy camp in Sirutheevu islet, killing 13 sailors and seizing weapons.

Tamilnet.com said the rebels did not suffer casualties. The site also reported two civilian deaths due to artillery fire in Jaffna, but did not say who fired the shells.

The military said 20 insurgents and one soldier were killed in fighting Wednesday in Jaffna and Welioya.

It was not possible to obtain independent confirmation of the reported fighting. Both sides often release contradictory versions of attacks that take place in the embattled north, where access is restricted.

Both sides are known to exaggerate death tolls and damage inflicted upon each other while underreporting their own losses.

Fighting has escalated in recent months along the front lines separating government-controlled territory and the Tamil Tiger rebels' de facto state in the north.

The government has pledged to capture rebel-held territory and crush the insurgents by the end of the year. Diplomats and other observers say the army has faced more resistance than expected.

The Tamil Tiger rebels have fought since 1983 to create an independent state for the island's ethnic minority Tamils who have suffered marginalization by successive governments controlled by majority ethnic Sinhalese.

More than 70,000 people have been killed in the conflict.