Hospital workers and members of the Tamil Rehabilitation Organization cover dead bodies on Wednesday at a makeshift hospital in the Tamil Tiger-controlled zone at Mullivaikaal, Sri Lanka. (Associated Press)

Sri Lanka pleaded for international help Thursday in an "emergency humanitarian situation," after a medical relief group warned that the number of civilian casualties is rising rapidly in the country's war zone despite the exodus of more than 100,000 in recent days.

Red Cross spokeswoman Sarasi Wijeratne said Wednesday about 1,000 badly wounded people were in desperate need of treatment or to be moved to better hospitals outside the conflict zone. Only two ill-equipped makeshift hospitals function in the tiny zone.

On Thursday, United Nations Secretary General Ban Ki-moon said he is sending a mission of experts to northeastern Sri Lanka to assess the deteriorating humanitarian situation for civilians.

The UN estimates that more than 4,500 civilians have been killed the past three months, and the Security Council expressed concern Wednesday at the plight of the civilians trapped in the tiny coastal strip still controlled by the Tamil Tigers.

The council asked the rebels to lay down their arms, renounce terrorism and join talks to end a 25-year civil war. It also urged the government to allow international agencies access to those affected by the fighting.

But despite its calls for help caring for those fleeing, the government did not say if it would let aid groups into the war zone. Since September, only the International Committee of the Red Cross has had access.

'About three-quarters of the injured coming in now have suffered from blast injuries, and the rest are gunshot wounds and mine explosions.'—Dr. Paul McMaster

Foreign Minister Rohitha Bogollagama did say, however, that the government was working to grant more access to those who had left the constantly shrinking strip of land, which now measures just 12 square kilometres.

The government says 102,790 civilians escaped the war zone this week, but 15,000 to 20,000 remain there.

Bogollagama called the flow of people from the region in the past few days an "emergency humanitarian situation.

"Our friends in the international community are most welcome to provide emergency relief assistance by way of semi-permanent shelter, water purification plants, sanitation facilities and medical assistance," he told reporters.

The medical aid group Doctors Without Borders said a growing number of badly wounded civilians suffering from blast injuries and gunshot wounds were arriving at a hospital near the zone.

"We've been seeing very severely wounded patients; the numbers of patients have increased rapidly over the last three or four days," Dr. Paul McMaster, a surgeon for Doctors Without Borders, said in an interview released by the Swiss-based group.

He said the 450-bed hospital now has more than 1,700 patients — many housed on the floors, in corridors and outside — and is close to being overwhelmed.

"About three-quarters of the injured coming in now have suffered from blast injuries, and the rest are gunshot wounds and mine explosions," McMaster said.

Troops in recent months have ousted the rebels from all their former strongholds and have hemmed them into what the government previously deemed a "no-fire" zone to protect civilians along the northeastern coast. But troops entered the zone this week to fight the remaining rebels and free trapped civilians.

They broke through a key rebel bunker on Monday, and tens of thousands of civilians have been fleeing the area since then. They are being held in government camps for screening.

Catherine Bragg, the UN's deputy humanitarian chief, said in New York that appeals to the government for access to the refugees and for permission to be present at the initial screening of refugees have received no response.

Access 'dependent on security situation'

Bogollagama, the Sri Lankan foreign minister, said access to those fleeing would be "dependent primarily on the security situation on the ground."

He said 14 international aid groups and UN agencies were helping to care for the displaced.

The government also has ignored calls to stop the fighting so more civilians could flee, saying it is on the verge of crushing the insurgency.

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

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.