Fighting has broken out between rival factions of Sri Lanka's Tamil Tiger rebels, with at least nine deaths reported. It is the first battle in the country since a truce two years ago brought a long-running civil war to a halt.

Military officials say mortar and heavy gun fire erupted early Friday across the narrow Verugal river, which divides fighters of the Tamil Tigers' main leadership from a breakaway faction in the east.

Within hours, the main Tiger leadership said its cadres had advanced on positions held by the rival faction. It said 300 fighters of the rival group had surrendered. The dead include rebels on both sides and an ambulance driver who was trying to evacuate the wounded. There is no independent confirmation of the claims.

The fighting broke out five weeks after the rebel movement, known for its iron discipline, suffered its first serious rift. The Tigers began fighting two decades ago for a separate homeland for the Tamil minority, but, in recent years, have said they would settle for greater autonomy.

Last month, commander V. Murilatharan, also known as Karuna, said he would lead his own faction, after complaining that the northern leadership was sidelining the eastern rebels.

The two sides have fortified their positions across the river in recent weeks, digging trenches and bunkers. About one-third of the Tiger force is under Karuna's command.

Jehan Perera, a political analyst with Colombo's National Peace Council, says the clash comes as no surprise, because leaders of the Liberation Tigers of Tamil Eelam - the LTTE - have quelled dissension ruthlessly in the past.

"Perhaps, it is in character with the LTTE's way of settling problems, because the LTTE has traditionally used physical, military force to eliminate those who opposed it," he said.

It is not clear who started the fighting. But Tamil Tiger leaders have denounced Karuna as a traitor, and vowed to get rid of him.

The Sri Lankan military has been put on high alert in the wake of the clashes among the rebels.

The fighting comes a week after Sri Lanka held a general election, in which the party of President Chandrika Kumaratunga won the most parliamentary seats.

The rebels say they want to revive peace talks that have been stalled for nearly a year with the new government, but that is unlikely to happen while the rift within the Tamil Tigers persists.