Rebels attacked a group of soldiers with guns in northern Vavuniya district on Monday sparking a clash, a defense official said on condition of anonymity, citing government regulations.
Soldiers confirm that four guerrillas were killed, he said.
Also Monday, soldiers in eastern Tincomalee district ambushed and killed three rebels, the official added.
Rebel spokesman Rasiah Ilanthirayan could not be contacted immediately for comment.
Violence has heightened in recent months around the rebels' northern ministate, which the government has vowed to dismantle. Four months ago the government announced that it has cleared the Eastern Province of rebels, even though small pockets of resistance remained.
Tamil Tigers have fought the government since 1983 to create an independent homeland for ethnic minority Tamils after historical discrimination by ethnic Sinhalese-controlled governments.
More than 70,000 people have been killed in the conflict.