Sri Lanka pleaded for international help Thursday to care for the 100,000 civilians who have fled a war zone.
Rohitha Bogollagama, the country's foreign minister, said Sri Lanka is facing an "emergency humanitarian situation."
He said Sri Lanka's government needs help to provide clean water, sanitation, medical care and shelter to the displaced.
The government has blocked most aid groups from entering the war zone since September.
But Bogollagama said Thursday it is allowing U.N. agencies and several other groups to help people who have left the zone.
Tens of thousands of people have fled the shrinking Tamil rebel enclave this week as the army prepares a final assault to end the country's 25-year-old civil war. The government says another 15,000 to 20,000 are still trapped inside the sliver of coastal land.
Late Wednesday, the U.N. Security Council late said it had "deep concern" for the welfare of those remaining inside the area held by the Liberation Tigers of Tamil Eelam.
Sri Lanka's military says troops now control all but five square miles of the Indian Ocean island, where the rebels and founder-leader Vellupillai Prabhakaran are fighting a last stand in their war to create a separate state for the Tamil minority.
United Nations spokesman Gordon Weiss said the world body had confirmed that between 90,000 and 100,000 people have left the combat zone since Monday. They will join 80,000 people already in refugee camps away from the front.
"There is serious overcrowding in the camps and it is only to get worse in coming days," Weiss said in Colombo. "It is a huge exodus and it threatens to overwhelm the available systems."
Military spokesman Brig. Udaya Nanayakkara denied rebel accusations that troops were shelling the area. "We are not using heavy weapons at all. We are only using small arms."
Independent confirmation of battlefield accounts is difficult because outsiders are generally restricted from it.
The people who have fled have been on foot for days, and stuck in the war zone with minimal food, water or medical care, aid agencies said.
Pictures released by the government showed scores of people carrying their belongings on their backs, and others helping the sick or elderly to move.
One showed a woman giving birth inside a bus carrying her to a refugee camp, with two midwives helping deliver the child.
The LTTE has said it will never surrender its fight to build a separate state for Tamils, which started in the early 1970s and erupted into a full civil war in 1983.
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