"People are being caught in the crossfire, hospitals and ambulances have been hit by shelling and several aid workers have been injured while evacuating the wounded. The violence is preventing the International Committee of the Red Cross (ICRC) from operating in the region," said Jacques de Maio, ICRC head of operations for South Asia in Geneva.

The terrified population is in need of protection, medical care and basic assistance, according to the ICRC.

An estimated 250,000 people are trapped in a 250 square-kilometre area which has come under intense fighting. They have no safe area to take shelter and are unable to flee.

"When the dust settles, we may see countless victims and a terrible humanitarian situation, unless civilians are protected and international humanitarian law is respected in all circumstances," said Mr de Maio. "It's high time to take decisive action and stop further bloodshed because time is running out."

The ICRC urgently appeals to both sides to allow and facilitate the safe and voluntary movement of civilians out of the combat zone.

The ICRC is determined to stay as long as possible in the Vanni, but the parties must respect its presence and its work. Humanitarian assistance must be allowed to enter the Vanni and aid workers and their premises must be protected from shelling and looting, as required by international humanitarian law.

Both sides are strongly urged to spare the lives of those not, or no longer, taking direct part in the fighting. Hundreds of patients need emergency treatment and evacuation to Vavuniya Hospital in the government-controlled area.

The ICRC, which is the only international aid agency to have remained permanently in the Vanni over the past four months with the agreement of both sides, continues to work alongside the Sri Lanka Red Cross Society helping those in need.