COLOMBO, Sri Lanka - Sri Lankan forces overran the Tamil Tigers' northernmost defence line Tuesday, forcing the rebels to retreat from one of their strongest fortifications, the military said.

The capture at Muhamalai on the Jaffna peninsula came as government forces continued to push the rebels deeper into their shrinking heartland in the northern jungles in hopes of finally crushing the insurgency.

Troops seized the insurgents' administrative capital of Kilinochchi last week, and the military said it was poised to seize the strategic base of Elephant Pass.

"Our forces are moving, and very confidently, and they are moving forward," defence spokesman Keheliya Rambukwella said.

He said the government hopes to clear the entire north of the rebels in the "coming weeks," effectively ending the 25-year-old civil war that has killed more than 70,000 people on this Indian Ocean island nation.

The rebels have been fighting to create an independent homeland for Tamils, who have suffered decades of marginalization by governments controlled by the Sinhalese majority.

In recent years, the Tamil Tigers controlled a de facto state in parts of the north of the country, while the government held the Jaffna peninsula to the north of rebel territory and the rest of the country to the south.

A recent government offensive from the south forced the rebels to abandon much of the land they held, but troops in Jaffna had been unable to break through the insurgents' heavily fortified northern lines at Muhamalai and open another front in the fight.

On Tuesday, government forces took control of the Muhamalai area and forced the rebels to fall back about 548 metres to another defence line, military spokesman Brig. Udaya Nanayakkara said.

The rebels offered less resistance than usual in the area, he said.

"They are withdrawing step by step," he said.

The rebels were not available for immediate comment. It is not possible to get independent accounts of the fighting because journalists are largely barred from the war zone.