Sri Lankan soldiers killed at least 180 elite Tamil Tiger fighters carrying out waves of counterattacks, and the pace of refugees fleeing the tiny war zone picked up speed, the military said today.

Heavy combat erupted over the weekend, suggesting the Liberation Tigers of Tamil Eelam (LTTE) were mounting a desperate defence against a military onslaught that has confined them to 17 square miles in the Indian Ocean island's northeast.

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Since Saturday, the LTTE's elite Charles Anthony Brigade and Radha Regiment have attempted to punch through the army's frontline, the military said.

"Now they have not held back. Their elite fighters have been deployed to stop troops from entering those areas," military spokesman Brigadier Udaya Nanayakkara said.

Nanayakkara said that a total of 180 bodies had been found since the weekend, including 80 today.

The LTTE appears to have saved its best-trained fighters for the final battle, he said. The Radha Regiment is the personal protection unit for LTTE leader Vellupillai Prabhakaran, whose whereabouts are unknown.

"There may be leaders confined in that area and they want to protect them. They are desperately fighting to prevent government troops from coming in," Nanayakkara said.

Also over the weekend, at least 676 civilians escaped the war zone, some on foot but the vast majority by boat, Nanayakkara said. The Red Cross estimates 150,000 people are still trapped, but the government says the number is no more than 70,000.

After 25 years of off-and-on civil war, Sri Lanka's military is racing toward a final battle to crush the separatist group as a conventional force.

The only thing slowing its advance is the presence of tens of thousands of civilians, mostly being held by the LTTE at gunpoint and suffering in what aid agencies say are dire conditions in a narrow coastal strip the army has declared a no-fire zone.

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Also today, the military said the LTTE fired artillery toward a ship flying the flag of the International Committee of the Red Cross (ICRC) that had landed food and aid supplies there.

The ICRC confirmed there had been shelling near the ship, which was not hit, and said the navy had ordered it to return to port because bad weather had made offloading cargo difficult.

"We have no reason to believe the cargo vessel was directly targeted," spokeswoman Sophie Romanens said. "It's a conflict zone so shelling is going on all over the place, so it is not possible to see who fired it."

The Tigers could not be reached for comment but has repeatedly denied accusations from witnesses and aid agencies that they have attacked civilians or fired artillery from inside the no-fire zone.

The pro-rebel website www.TamilNet.com, quoting an unnamed source, reported the LTTE had launched an artillery attack over the weekend that killed a "considerable number of soldiers".

Nanayakkara acknowledged some soldiers had been killed: "We have suffered casualties, but we are not releasing the numbers."

Both sides in the past have distorted battlefield figures to their advantage, and independent confirmation is difficult since the war zone is normally sealed off to outside observers.

The LTTE since 1983 has fought a civil war to create a separate homeland for Sri Lanka's Tamil minority, which complains of mistreatment by successive governments led by the Sinhalese ethnic majority since independence from Britain in 1948.