Fighting in the last two days has centered on the rebels' Thoppigala base, one of their last redoubts in the area, which has proved difficult for the government to conquer due to a huge rock formation that provides perfect cover for rebel fighters during combat.

The army said the deadly mortar fire came from this base.

``We are left with no option but to intensify our operations to silence their guns,'' Samarasinghe said.

Eight Tamil civilians who had taken cover in a government-controlled area were killed and 18 more wounded, said senior official Lt. Col. Upali Rajapakse.

He said the army was trying to evacuate the wounded but hampered by continuing mortar fire.

However, Tamil Tiger military spokesman Rasiah Ilanthirayan said it was the military who had been shelling the area as part of its offensive.

TamilNet, a pro-rebel Web site, said the dead included three siblings aged 2, 15 and 18.

Local police officer H. M. D. Herath confirmed at least 2 children were among the dead.

It was not possible to independently verify the claims and both sides frequently blame each other for civilian deaths.

In Vavuniya, Samarasinghe said the roadside bomb a favored weapon of the rebels hit a tractor the troops were traveling on to deliver food to comrades.

Sri Lanka - 's undeclared war took on heightened drama this week, with the rebels' first airstrike of the conflict Monday, a suicide bombing at a military camp Tuesday and a naval battle off the eastern coast on Thursday.

Sri Lankan navy ships intercepted a flotilla of Tamil Tiger boats during Thursday's three-hour sea battle, sinking three of them and killing at least 16 rebels.

The rebels launched their fight for an independent homeland for the country's 3.1 million Tamils in 1983 after decades of discrimination by the majority Sinhalese. In the years since, they have pioneered the use of suicide bomb belts and slowly built up a navy of small gunboats.

Hopes for peace that followed the 2002 ceasefire have been dashed in the past 18 months as sporadic shootings and bombings have grown into an all-out war in eastern and northern Sri Lanka - , where the Tigers want to establish their separate state.

An estimated 69,000 people have been killed in the violence.Discuss this story Published: Fri Mar 30 07:29:47 EDT 2007