The report accuses the government of denying humanitarian assistance to Tamils civilians [EPA]

A UN report has found "credible allegations" that tens of thousands of civilians were killed and that war crimes were committed during the final months of Sri Lanka's conflict with the Tamil Tigers.

A leaked excerpt from the report, drafted by a panel appointed by Ban Ki-moon, the UN secretary-general, made its way into Sri Lankan newspapers on Monday.

"The panel found credible allegations, which if proven, indicate that a wide range of serious violations of international humanitarian law and international human rights law," the report says.

The report says that war crimes were possibly committed by both the Sri Lankan government and the Tamil Tigers, also known as the Liberation Tigers of Tamil Eelam (LTTE), during the decades-long civil conflict in the Indian Ocean island.

Extracts incomplete

The UN has confirmed the report, but has stressed that the extracts are incomplete.

"The United Nations says the excerpts ... don't include some of the more positive aspects of the government's conduct, but that really doesn't change these damning findings," Kristen Saloomey, Al Jazeera's correspondent at the UN, said.

"What the report apparently finds - and we haven't seen the official copy - is that the government was responsible for most of the civilian casualties in this conflict."

The report also accuses the Sri Lankan government of denying humanitarian assistance to the Tamils and of silencing media critical of its policies.

It specifically accuses the government of widespread shelling including the targeting of field hospitals and rights violations against people inside and outside the conflict zone.

Sri Lanka's government reacted angrily to the excerpts.

"The report is a fraud and biased and we reject it," Keheliya Rambukwella, a government spokesman, said.

"We are not panicked, and even we made our protest when they appointed the panel with regard to their mandate. Our stand has not changed."

Sri Lanka refused to co-operate during the compiling of the report, with the government of Mahinda Rajapaksa refusing to let the panel into the country as it prepared its report.

Investigation urged

The government has consistently denied allegations that it targeted civilians in its conflict with the LTTE.

But it has acknowledged that some were killed as troops advanced on an ever-shrinking patch of land on the northeastern coast of the country.

The report calls for an investigation, saying: "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."

But the elimination of the LTTE leadership by the government in May 2009 means that only government forces would be able to be held accountable should any inquiry arise.

The LTTE fought for a separate state for Sri Lanka's minority Tamils, who have complained of persecution by successive governments dominated by the Sinhalese majority since independence from Britain in 1948.