At least 71 people were killed in one of the bloodiest days of combat since Sri Lanka's armed forces intensified a thrust into rebel-held turf three months ago, the military said on Thursday.
Most of the deaths came from a battle on Wednesday near the northwestern fishing port of Nachikkudah, about 300 km (185 miles) north of the capital Colombo, which killed 40 Liberation Tigers of Tamil Eelam (LTTE) and 10 soldiers, the military said.
Nachikkudah has been the scene of heavy fighting for weeks, with ground troops pushing forward and air force jets pummelling LTTE bunkers and outposts with almost daily air strikes.
"Heavy fighting occurred throughout the day on Wednesday and the troops managed to successfully secure an area of 1.5 km of the LTTE's Nachikkudah forward defence line," said a spokesman at the state-run Media Centre for National Security, asking not to be named in line with the policy.
At least 27 soldiers and 30 rebels were wounded in the fighting.
There was no independent confirmation of the casualties and the rebels could not be reached for comment.
Fighting elsewhere across the Indian Ocean island nation's north also killed 20 more insurgents and wounded 25. An additional soldier was killed and another six were wounded, the spokesman said.
On Tuesday the military said they were within 5.5 km (3 miles) of Kilinochchi town, the LTTE's de facto capital and a prized target as Sri Lanka's military tries to wipe out a foe it has battled since 1983.