The two sides claimed to have inflicted heavy casualties in the weekend fighting with the military saying at least 16 government soldiers and three rebels were killed.

The rebel Liberation Tigers of Tamil Eelam (LTTE) said they resisted a two-pronged military assault and captured several bodies of Sri Lankan soldiers killed in the pre-dawn fighting.

"More than 16 Sri Lanka army troops were killed and around 45 others were injured in the clashes," the Tigers said in a statement.

The defence ministry admitted heavy fighting and placed its own losses at least 10 soldiers killed and 34 wounded. The ministry said "a large number" of Tigers were also killed.

Meanwhile, four civilians were bound and shot dead execution-style in northern Sri Lanka near the scene of heavy battles between troops and Tamil rebels, a police official said Sunday.

The bodies of the four were found shot in the head Sunday with their hands tied behind their backs in Vavuniya district.

"Four people were found shot dead at Tavasakulam in Vavuniya," said a police official in Vavuniya, 260km north of Colombo.

"An investigation is under way," he said adding that it was unclear who was behind the killings.

The four were killed in the same region where security forces and the rebel Liberation Tigers of Tamil Eelam (LTTE) fought pitched battles on Saturday, officials said.

Sri Lankan troops used war planes and long-range weapons to attack suspected Tamil Tiger positions as fresh fighting broke out early Saturday, the ministry said.

Fighter jets pounded suspected LTTE locations in the north of the island to back the ground offensive.

Both sides traded heavy weapons fire across a defence line in Vavuniya district, the ministry said.

The clash Saturday at Thampanai came three days after security forces wrested control over the final rebel base in the east of the island.

The LTTE admitted on Thursday losing Thoppigala in the district of Batticaloa, but said it would now would revert to guerrilla tactics in the troubled region.

Fighting across Sri Lanka has worsened since the breakdown of a 2002 truce around 19 months ago.

Sri Lanka's 35-year-old conflict has claimed more than 60,000 lives, and over 5,200 people have been killed in fighting in the past 19 months, according to government figures.

The rebels are fighting for an independent homeland for the Tamil minority on the Sinhalese-majority island.