A UN panel has called for an independent inquiry into "credible" allegations that Sri Lanka committed war crimes and crimes against humanity in its final 2009 offensive against Tamil Tiger rebels.

The panel of experts, appointed by UN Secretary General Ban Ki-moon, submitted its report last week, and leaked excerpts were published Saturday in Sri Lanka's pro-government Island newspaper.

The leaked report detailed "credible allegations" which, if proven, indicate a wide range of violations by both the government and the rebels, "some of which would amount to war crimes and crimes against humanity".

Specifically, it cited charges of government shelling that knowingly targeted civilians and hospitals in "no-fire zones", as well as the denial of humanitarian assistance to victims of the fighting.

It said "tens of thousands" of people died between January and May 2009 in the final government offensive that resulted in the defeat of the separatist Liberation Tigers of Tamil Eelam (LTTE), ending a decades-old ethnic conflict.

"Most of the civilian casualties in the final phases of the war were caused by government shelling," the leaked document said.

It also listed alleged violations by the rebel forces, saying they had intentionally used civilians as human shields.

"The LTTE started point-blank shooting of civilians who attempted to escape the conflict zone, significantly adding to the death toll in the final stages of the war," it said.

The report also rapped UN political bodies for not doing enough to protect civilians during the final stages of the brutal war.

A copy of the panel's report, which the UN had scheduled for release next week, had been sent to the Sri Lankan government, which responded last Wednesday by calling it "fundamentally flawed" and "biased".

Observers suggested Colombo may have engineered the leak to prepare a full rebuttal that would pre-empt the report's official publication.

A foreign ministry official confirmed the leaked document was genuine and said the foreign minister would brief diplomats in Colombo on the specific allegations next week.

In New York, a UN spokesman described the leak as "deeply regrettable".

Sri Lanka, which has vehemently denied any war crimes, had protested the creation of the UN panel and refused to allow its three members -- led by former Indonesian attorney general Marzuki Darusman -- to visit the country.

To a large extent, the report is a compendium of allegations that have already been made against the government and the rebels by UN agencies, humanitarian organisations such as the Red Cross, and human rights groups.

Its conclusions will increase the pressure on Ban to order an independent war crimes inquiry -- a move which Sri Lanka has said it would firmly oppose.

"These credibly alleged violations demand a serious investigation and the prosecution of those responsible," the leaked report said.

"If proven, those most responsible, including Sri Lanka army commanders and senior government officials, as well as military and civilian LTTE leaders, would bear criminal liability for international crimes," it said.

Labelling a Sri Lankan government commission set up to investigate the handling of the conflict "deeply flawed", the experts said Ban should immediately set up "an independent international mechanism" of inquiry.

Source: AFP Asian Edition