The United Nations said Friday that hundreds of men identified by residents as "janjaweed" militia forces killed about 50 civilians in an attack this week on Darfur villages in the latest atrocity that can be linked to the Sudanese government.

"At the very least, the attacks demonstrated the government of Sudan's continued failure to disarm militia in Darfur, and at worst its use of militia forces that target civilian populations," said a U.N. human rights report released in Geneva.

The report, compiled by U.N. officials in Sudan and released by the U.N. High Commissioner for Human Rights, said the majority of those killed in the Oct. 29 attack were young boys and elderly men.

The attacks on seven villages and a refugee camp in Western Darfur came to light Thursday when they were condemned by U.N. Secretary-General Kofi Annan, whose spokesman Stephane Dujarric said the violence had "caused scores of civilian deaths and forced thousands to flee the area."

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The report said that there were "troubling indications that Sudanese military personnel may have participated in the attacks, based on descriptions of some of the attackers."

It said witnesses identified the attackers as Arabs riding on horseback, wearing green camouflage military uniforms and armed with Kalashnikov assault rifles and rocket-propelled grenades.

"It appears their total number was between 300 and 500," the report said. "Witnesses also saw three men with the insignia of commissioned Sudanese Armed Forces military officers."

The government has always denied backing the janjaweed. But U.N. investigators have found that the government armed the janjaweed, and members of the militia have acknowledged receiving state support.

Government officials could not be reached for comment on Friday, the beginning of the weekend in Sudan.

More than 200,000 people have been killed and 2.5 million others displaced since the conflict began in February 2003, when Darfur's ethnic African tribesmen took up arms against what they saw as decades of neglect and discrimination by the Arab government in Khartoum.

A peace agreement signed by the government and one rebel group in May has been ignored, and the violence has escalated in recent months. The accord committed the government to disarming the janjaweed.

Earlier Friday, two U.N. officials blamed the attacks on the janjaweed, but spoke on condition of anonymity because of the sensitivity of the issue. Last month, Sudan's government expelled chief U.N. envoy Jan Pronk after he said on his personal Web site that government forces had suffered defeats in Darfur and were deploying militia and troops to the western region in defiance of U.N. Security Council resolutions.

An official with the African Union peacekeeping force in the region said thousands of civilians were fleeing the Jebel Moon area where the attack occurred in fear of further violence.

The U.N. mission in Sudan said in an Internet statement Friday that the state-appointed governor of Western Darfur had agreed to investigate the attacks. A delegation comprising "state authorities and at least one community leader" had already visited one village, Silea, to begin the inquiry, the U.N. statement said.

The U.N. Security Council voted in August to replace the African Union's 7,000 troops trying to protect civilians in Darfur with 20,000 U.N. peacekeepers.

But Sudan's President Omar al-Bashir has refused to allow their deployment, saying they would be "neocolonialists."

In Beijing on Friday for the China-Africa summit, al-Bashir told reporters that his government will not relent on its rejection of U.N. peacekeeping troops for Darfur.

Al-Bashir said allowing U.N. troops into Darfur would lead to a greater number of deaths, likening it to the peacekeeping situation in Iraq.

"We refuse to accept the entry of U.N. peacekeepers into Sudan because the impact of our refusal is better than the impact of our acceptance," al-Bashir said, speaking in Arabic at a news conference. "We dare not think of what the consequences would be of them being there."