Geneva - The situation in northern Sri Lanka is "desperate," United Nation's top human rights official Navi Pillay said Friday, criticizing both the government and the Tamil rebels.

"The current level of civilian casualties is truly shocking, and there are legitimate fears that the loss of life may reach catastrophic levels, if the fighting continues in this way," Pillay, the UN High Commissioner for Human Rights, said.

"Certain actions being undertaken by the Sri Lankan military and by the LTTE may constitute violations of international human rights and humanitarian law," the South African jurist said.

Pillay said the government was shelling zones it declared to be "no fire" areas, placing civilians at risk.

"Close to 500 people were reportedly killed and more than a thousand injured in these zones" in the last three weeks, her office said in a statement.

According to Pillay's sources more than 2,800 civilians may have been killed and more than 7,000 injured since 20 January.

According to UN estimates, a total of 150,000 to 180,000 civilians remain trapped in tony bit of land in the Vanni region, which was constantly shrinking as government forces made progress.

She also condemned sharply the Tamil Tiger rebels for forcing civilians to remain in the conflict zone and possibility recruiting child soldiers.

"The brutal and inhuman treatment of civilians by the LTTE is utterly reprehensible, and should be examined to see if it constitutes war crimes," said Pillay.

Both sides to the conflict should stop hostilities to allow for civilians to evacuate the danger zones and the government should let aid agencies enter those areas, she said.

Heavy fighting continued Friday morning in the north on Friday. (dpa)