Suspected Tamil Tiger rebels shot dead at least 10 people in southern Sri Lanka, the military said on Friday, two days after 27 people were killed in a bus ambush in a nearby town.

A six-year truce between the state and rebels formally ended on Wednesday, opening the way for a military push for the Tigers' northern stronghold and a bloody escalation in a 25-year civil war, analysts say.

"The clearing troops found total of 10 people shot and killed by the LTTE in Thanamalwila including two police personnel," said military spokesman Brigadier Udaya Nanayakkara. Thanamalwila is near the town of Buttala where the bus ambush took place.

Air force fighter jets bombed a Tamil Tiger rebel arm storage complex in the Tiger stronghold of Mullaittivu district on Friday the military said, but no further details were given.

The Tigers were not immediately available for comment on the attacks and air raid.

The military said most of the 27 people killed in Wednesday's bus ambush were shot by rebels as the passengers tried to flee, rather than in the bomb blast that struck the vehicle, and Tiger fighters shot dead six farmers while returning after the attack.

The Sri Lankan government scrapped the 2002 truce a fortnight ago, deepening fears of an escalation in the fighting.

The military said more than 40 civilians, 23 soldiers and over 200 rebels have been killed from fighting since then. About 70,000 people have been killed since the war erupted in 1983.