An exodus of civilians fleeing the fighting in northern Sri Lanka has picked up, with more than 1,500 escaping in the last day, the government said Wednesday.

Tens of thousands of civilians are trapped in a sliver of land along the island's northeast coast where government troops are battling to dislodge remnants of the Tamil Tiger rebels.

A statement on the government's website said 1,515 people, including nearly 650 children, had crossed into military-controlled areas by late Tuesday near Puthkkudiyirippu, where battles between government troops and the rebels have been raging for weeks.

Puthkkudiyirippu is the last town held by the rebels, who have been fighting since 1983 for a separate Tamil state in the island's north and east.

The statement said the civilians were being screened and would be taken to displacement camps in the interior of the island.

The military also said its troops captured a safe house belonging to Pottu Amman, the powerful intelligence chief of the rebels.

Independent accounts of the fighting are not possible because access to the area is restricted.

There has been a surge in civilians fleeing the area recently as the army pushes forward with an all-out offensive the government hopes will soon end the island's 25-year-old civil war.

The rebel holdouts, along with tens of thousands of terrified civilians, are confined to about 28 square kilometres of jungle and beach on the northeastern coast.

Risks to the civilians have led the United Nations, European Union and numerous countries to voice concern.

The UN has said 2,800 civilians caught in the fighting have been killed since late January, though the government disputes that figure.

The UN estimates at least 150,000 civilians are trapped. The government says the number is closer to 50,000 to 60,000, and accuses the rebels of using them as human shields in a bid to avoid defeat.

The military also said Wednesday that suspected Tamil rebels shot dead five farmers and wounded two others in a village in eastern Sri Lanka. No reason was given for the attack.

The rebels could not be reached for comment since communication with their stronghold has been severed.

The rebels have been fighting since 1983 for an independent state for the Tamil minority, which suffered decades of marginalization at the hands of governments dominated by the Sinhalese majority. More than 70,000 people have been killed in the fighting.