Sri Lankan military officials said the main Liberation Tigers of Tamil Eelam (LTTE) mounted an attack on a breakaway faction in the east of the island early on Monday.
"Initial reports say that two fighters of the northern faction were killed in the clash,and three members of the eastern group were wounded," said a military spokesman.
Police in the town of Welikanda, where the clash took place, said they had recovered two bodies from the scene.
Diplomatic sources said the clashes between the Tigers and a breakaway faction led by V Muralitharan, better known as Karuna, have cast a shadow over Norway's peace efforts.
Karuna, the de facto number two in the LTTE, led a split in the Tigers in March last year and since then the main guerrilla outfit has been trying to retake control over the east where the renegades are active.
The LTTE has accused Sri Lankan security forces of colluding with the breakaway group, an allegation rejected by the government.
The Tamil Tigers began fighting for a separate homeland for minority Tamils in 1983.
More than 65,000 people were killed in the civil war until Norway negotiated a ceasefire in 2002.
Subsequent peace talks broke down in April 2003 when the Tigers withdrew, demanding more autonomy for Tamil-majority areas.