Colombo: At least 29 people were killed in a roadside bomb blast and clashes between security forces and Tamil Tiger rebels in Sri Lanka's embattled north, military officials said.

Two soldiers were killed when a roadside blast carried out by the Tigers targeted a military bus in the Jaffna peninsula on Friday night, they said.

The attack came as the military shot dead 10 Tiger rebels who tried to break into an army defence line in the same area, the officials said.

In a separate incident, six Tiger rebels and three soldiers were killed in a gunfight in the district of Vavuniya, where another eight guerrillas died in two separate clashes, they said.

The latest upsurge in fighting came as the security forces strengthened their hold in the east of the island.