Two Tamil Tiger officials surrendered to the Sri Lankan army on Wednesday, and refugees joined a stream of more than 80,000 people the government says have fled a war zone that appeared to shrink by the hour.

The sandy beaches north of the tiny combat zone — which now measures just five miles long — were filled with people carrying their belongings on their backs or in bundles on their heads, according to photos released by the military. Mothers held infants and others carried sick relatives as they reached government territory in boats escorted by the navy.

In a sign that the rebel leadership has begun to feel the military pressure, the rebels' former media spokesman Velayutham Dayanithi, whose nom de guerre is Daya Master, and an interpreter for group's political wing, known only as George, turned themselves over to government forces Wednesday. The two played prominent roles in talking to the media and visiting foreign diplomats in a now defunct peace process.

The former spokesman is the most senior rebel official to surrender so far, military spokesman Brig. Udaya Nanayakkara said. The remaining rebels were still resisting the army's advance, he said.

There were casualties among government troops, but Nanayakkara did not provide details.

The U.N. and humanitarian groups called for an immediate stop to the fighting, so more civilians could escape. Over the past three days, the military says more than 80,000 have fled after forces broke through a key rebel embankment protecting their territory.

The government has ignored calls to stop the fighting, saying for weeks it was on the verge of crushing the rebels as troops ousted the them from their former strongholds and hemmed them into a tiny strip of coastal land.

The government had previously deemed that area a "no fire" zone to protect civilians. But troops broke through the embankment, entered the zone and captured part of it during fighting Monday and Tuesday. At least 43 rebels were killed, Nanayakkara said.

The U.N. estimates that more than 4,500 civilians have been killed in the past three months.

On Tuesday, the rebels accused the government of killing 1,000 civilians in their latest offensive — a charge the military denies. In the past, humanitarian groups have said troops shelled the densely populated area.

Dr. Thangamuttu Sathyamurthi, one of the few doctors working in the war zone, said the bodies of 80 civilians were brought to two makeshift hospitals soon after Monday's raid but said more people would have died and been buried on the spot.

"I think more people would have been killed, we saw only 80 bodies but people have seen a lot more people dead on the roads," he said, adding one of his fellow doctors was also among the dead.

Fighting continued Wednesday and shells fell near a Roman Catholic church wounding a priest and killing three civilians who had pitched their tents in the church compound, Sathyamurthi said.

The military denies targeting the civilians or using heavy weapons at populated areas.

"We suffered casualties because we are not using heavy and long-range weapons. We only use small weapons," Nanayakkara said, accusing the rebels of firing artillery shells.

It is not possible to confirm accounts from the war zone because independent journalists are barred from entering it.

Human rights groups accuse the rebels of holding civilians against their will and using them as human shields, and accuse the government of indiscriminate shelling in the region. Both sides deny the allegations.

The United Nations, many countries and human rights groups have expressed grave concerns for the remaining trapped civilians, fearing the government may launch an all-out assault soon after giving the rebels a 24-hour ultimatum to surrender.

The deadline expired Tuesday with no response from the rebels.

About 3,000 demonstrators gathered on Wednesday outside Britain's Parliament to call for an immediate cease-fire, following days of continuous protest, police said.

British Prime Minister Gordon Brown's office says he'll meet lawmakers to discuss the conflict and the demonstrations. The pro-Tamil protests have included hunger strikes and several incidents in which demonstrators have attempted to set themselves on fire.

Amnesty International urged the government and rebels on Wednesday to halt the fighting. "The security of civilians trapped between Sri Lankan forces and the Tamil Tigers is paramount," said Yolanda Foster, the group's Sri Lanka expert.

The rebels have been fighting to create an independent homeland for ethnic minority Tamils, who have faced decades of marginalization by successive governments controlled by ethnic Sinhalese. More than 70,000 people have been killed in the violence.