Government war planes bombed positions of the Liberation Tigers of Tamil Eelam (LTTE) in the district of Batticaloa on Tuesday.
"We have taken identified LTTE targets in Batticaloa today," said Keheliya Rambukwella, the government's defence spokesman. He did not give any information on any casualties.
Hours later, Tiger rebels fired mortar bombs at the army's front line in the northern peninsula of Jaffna as the military accompanied reporters and photographers to positions where the security forces have made recent gains.
Military officials in Jaffna said four soldiers were killed and at least eight others were wounded.
The fighting follows an announcement by peace broker Norway that the two sides had agreed to meet for talks for the first time since the rebels pulled out of negotiations in April.
The attacks came a day after both sides accused each other of the massacre of 10 Muslim men in the neighbouring district of Ampara on Monday.
Rambukwella said authorities were sending investigators to Ampara where the labourers were found hacked to death.
"We want to get to the bottom of this," Rambukwella said. "The circumstantial evidence suggests it is the LTTE, but if anyone of us is involved, we will mete out maximum punishment."
The massacre came a day after the Sri Lankan navy and the air force bombed an unnamed vessel said to be transporting weapons and ammunition for the rebels off the coast of Ampara.
In Panama, eastern Sri Lanka, there were sporadic clashes between groups of stone-throwing Muslim youths and security forces. Local residents blame the security forces for the massacre of the 10 labourers.
The pro-Tiger website www.tamilnet.com said on Tuesday that the only survivor of the massacre had died of his injuries.
A government spokesman denied this. "He is in intensive care, but we expect that he will be able to provide a fuller statement in the coming days," he said.
Rauff Hakeem, leader of the Sri Lanka Muslim Congress, called for a thorough investigation into the killings, which took place in a government-held area not known for a strong Tiger presence.
"The perpetrators of this horrendous act, whoever they are, should be punished severely," he said in a statement.
Tamil rebels have waged a drawn-out insurgency for a separate ethnic homeland in Sri Lanka, a majority Sinhalese nation. More than 60,000 people have died since the rebellion began in 1972.