Colombo - The United Nations Monday expressed concern about the welfare of civilians and its staff members caught in fighting in northern Sri Lanka between government troops and Tamil rebels.

The UN said that, though a designated safe zone - a 12 kilometre stretch on the coastal line in the north east - had provided some respite to tens of thousands of civilians caught up in the conflict, reports received on Sunday indicate that fighting was reported inside the zone.

The UN office in Colombo said the fighting had led to the deaths and injury of more civilians, but did not specify the number killed or injured.

The organization said it "calls the Lankan forces and the LTTE (Tamil rebels of the Liberation Tigers of Tamil Eelam) to refrain from fighting in areas of civilian concentration".

It blamed the rebels for continuing to "actively prevent" people from leaving the war zone by shooting and injuring those trying to reach government-controlled areas.

Those trapped included 15 UN staff members and 75 of their dependents, consisting of 40 children and 35 women. It did not say if any foreign staff members were included in that tally.

The UN said that one staff member had been forcibly recruited into the LTTE on Sunday and that it was making an urgent appeal for his release. It also called for the LTTE to stop forcibly recruiting civilians.

"Tens of thousands of civilians remain in the 'Vanni Pocket,' (the areas of fighting in north eastern Sri Lanka) including a large number of children. They are experiencing serious shortages of food, medicine, and clean water, and, as a result, increasing numbers are becoming ill.

"Efforts to bring in more food and medicines have not yet been successful and it is imperative that these needs be met," the UN statement said.

Some 34,000 civilians have already left the rebel-held areas and are being accommodated in government welfare centres.

At least 100,000 civilians remained trapped in the rebel- controlled area, which is limited to some 150 square kilometers. Government troops are continuing operations to recapture the area.

The military says they have entered the final phase of a 25-year battle aimed at subduing the rebels. Vast parts of rebel-held areas have been recaptured by troops in a series of offensives launched since August 2006. (dpa)