Aerial view of the coastal strip, a former war zone where the Tamil rebels made their last stand, videotaped by VOA

Amnesty International is calling on the United Nations to make public what it knows about civilian deaths in Sri Lanka during the final stages of the government's assault on Tamil Tiger rebels.

The human-rights group challenged the U.N. Friday to disclose a full account of how many civilians were killed, following a British newspaper report that up to 20,000 civilians died during the final weeks of fighting, and that most were killed by Sri Lankan government forces.

According to The Times of London, details of the casualties in Sri Lanka came from confidential U.N. sources, who said many of the deaths were due to indiscriminate shelling.

The United Nations has declined to confirm the newspaper report. In Sri Lanka, government officials say the account was inaccurate; they say Tamil rebels were to blame for any civilian deaths.

In a statement Friday, Amnesty International said its information indicates there was a "bloodbath" in northeast Sri Lanka earlier this month.

U.N. officials have previously estimated at least 7,000 civilians were killed in the final assault on rebel-held territory in northeast Sri Lanka.

Amnesty sharply criticized the U.N. Human Rights Council for deciding earlier this week not to investigate recent events in Sri Lanka. The rights group is calling for an independent, international investigation of what it calls apparent war crimes committed by both sides.

Amnesty says it has received consistent reports of widespread and serious human-rights violations in the conflict zone, including enforced disappearance, extrajudicial executions, torture and sexual violence against those displaced by the war.

The media-rights group Reporters Without Borders urged the Sri Lankan government Friday to allow journalists to enter camps for the hundreds of thousands of people displaced by the fighting. It also expressed concern over statements by Sri Lankan authorities saying journalists who traveled to rebel-held areas during the war would be prosecuted.

The government's victory over Tamil Tiger rebels this month appears to have ended 25 years of civil war.

The Tamil Tiger rebels began their fight for a separate homeland for the ethnic Tamil minority in 1983. Since then, the U.N. estimates the conflict has killed as many as 100,000 people.