COLOMBO, Sri Lanka - Two senior Tamil Tiger officials surrendered to the Sri Lankan army 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 eight kilometres 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 United Nations 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.

Britain and France said Wednesday they're pressing for more international help for civilians, including perhaps sending boats for an evacuation mission.

The charity Save the Children warned that the exodus was far from over. "The next few days are crucial as more people who are trapped in the conflict zone are expected to come out in large numbers," Prasant Naik, the British-based group's director for Sri Lanka, said in a statement.

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 UN estimates that more than 4,500 civilians have been killed in the past three months, but the world body, like all aid groups, has no access to the densely populated strip of land.

In the past few months, the UN has monitored satellite images from the region, counting the number of shelters in an effort to estimate how many civilians have been displaced by fighting. On Tuesday, the U.S. government released satellite images showing about 25,000 tents for civilians squeezed into the rebel territory.

Journalists, too, are barred from the area, and thus the rebels and military have traded accusations that are virtually impossible to verify. The allegations, themselves, have become part of the conflict, as each side tries to control the story.

On Tuesday, the rebels accused the government of killing 1,000 civilians in their latest offensive -- a charge the military denies.

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.

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.

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.