Brigadier Prasad Samarasinghe, a military spokesman, said on Friday that the Tigers launched an attack on a military camp in Mankerni in Batticaloa district early in the morning.
The army, supported by fighter helicopters, repulsed the rebel attack, he said.
Samarasinghe said a large number of rebel bodies were lying on the battlefield, but that exact details were unavailable.
In the northern Jaffna Peninsula, six soldiers were wounded on Friday when Tamil Tigers fired artillery toward the northern defence line, the military spokesman said.
The air force later launched air strikes on rebel artillery and mortar positions, Samarasinghe added.
Separately, soldiers destroyed six Tamil Tiger boats suspected of transporting fuel off the country's northern coast, he said.
Peace in jeopardy
The fighting came a day after the government said it is ready to resume stalled peace talks with the Tamil rebels later this month in Switzerland.
A round of peace talks is planned for October 28 and 29 in Switzerland.
The last round of peace talks, aimed at ending two decades of civil war, was held in February.
Nordic cease-fire monitors said the clashes put the talks into "jeopardy".
Separately, 49 Tamil Tiger rebels were killed on Friday in a raid by a breakaway faction in eastern Sri Lanka, a spokesman for the breakaway group said.
The group, known as the K-faction, overran three Tamil Tiger camps in the Vaharai area of eastern Batticaloa district, killing 49 mainstream rebels, a spokesman said.
It was not immediately possible to verify the claim independently.