As battles between the two sides persisted and authorities maintained an alert in Colombo following rebel bombings, the military was forced to send 600 troops to state hospitals to fill in for striking health workers, military spokesman Brig. Udaya Nanayakkara said.
"This is a drain to the army ... This is a bad time for this to be happening," he said, adding that most of those sent were support staff and not essential to the war effort.
The rebels have been fighting since 1983 for an independent homeland for minority Tamils in Sri Lanka's north and east following decades of discrimination under government dominated by the Sinhalese majority. More than 70,000 people have been killed in the conflict.
A 2002 cease-fire agreement fell apart over the past two years. Fighting has intensified in recent months along the front lines separating government troops from the rebels' de facto state in the north, and senior officials have called for an all out offensive to destroy the Tamil Tigers.
About 7 a.m. Wednesday, Tamil Tiger fighters in the Mannar district south of rebel-held territory attacked a group of soldiers guarding a key road, killing three soldiers, Nanayakkara said. Troops retaliated and drove the rebels back into the jungle, he said.
The attack came a day after rebel fighters attacked troops at a different point in the Mannar area in a gunbattle that killed seven guerrillas, he said Wednesday. No troops were killed in that battle, he said. Two other battles Tuesday in the Jaffna peninsula north of rebel territory killed 13 insurgents and two soldiers, the military said.
Since Saturday, 123 rebels and 17 soldiers have been killed, according to military figures.
Rebel spokesman Rasiah Ilanthirayan did not answer calls for comment, though he has disputed the military's figures in recent days. Each side routinely exaggerates the other's casualty numbers and plays down its own, and independent confirmation of the death tolls is unavailable due to restricted access to the conflict zone.
Meanwhile, Sri Lankan authorities, facing a groundswell of criticism, released most of the Tamils detained in a security crackdown following twin bombings last week that killed 20 people and were blamed on the Tamil Tigers, said Cabinet minister Jeyaraj Fernandopulle.
By Tuesday afternoon, the government had released all but 202 of the 2,554 people detained in the security sweep in Colombo and its suburbs, he said.
"This is not an action taken against a minority. This is about security and the government safeguarding people in the town," Fernandopulle said.
Tamils have repeatedly complained of discrimination at the hands of the security forces, which are dominated by ethnic Sinhalese.
"They are desperate, and they think every Tamil is a terrorist ... that's why they are doing random arrests," said Kanagalingam Sivajilingam, a lawmaker for the Tamil National Alliance party. "We are very angry. People are so angry."
A coalition of human rights groups condemned the detentions, saying many were not told why they were detained and their relatives were not informed - a violation of presidential guidelines.
Amnesty International said it was deeply concerned that "the arrests have been made on arbitrary and discriminatory grounds using sweeping powers granted by the emergency regulations."
The regulations give authorities wide-ranging powers to arrest terror suspects and detain them indefinitely.