Colombo - Government troops entered a rebel stronghold in northern Sri Lanka, killing at least 25 Tamil rebels, a military spokesman said Thursday.

Troops advanced to the Mallavai area, 320 kilometres north of Colombo, penetrating as far as the Mullaitivu district where rebel leader Velupillai Prabhakaran had been living, Brigadier Udaya Nanayakkara said.

During the operation troops killed 25 rebels and captured an irrigation tank as well as three mortars, the spokesman said.

The operation came as the Tamil rebels announced a unilateral cease-fire from July 26 to August 4 to mark the eight-nation South Asian regional summit taking place in Colombo during that period.

The government has rejected the truce and said any peace moves by the rebels can be accepted only if they lay down their weapons. (dpa)