The small patrol of African Union peacekeepers were struggling with two stranded cars near this Darfur refugee camp when the Arab militiamen sped by in trucks, shouting and brandishing weapons. They were the Janjaweed, the fierce militiamen accused of raping and murdering African villagers and turning western Sudan's Darfur region into one of the world's gravest humanitarian crises.

The incident — witnessed Wednesday by a reporter for The Associated Press — shows how little the Janjaweed fear the understaffed and underfunded African Union peacekeeping force, which is supposed to monitor a cease-fire and protect civilians here.

Sudan has refused to allow the United Nations to send in peacekeepers to replace the AU force and protect civilians.

CountryWatch: Sudan

In the Wednesday incident, a half-dozen pickup trucks mounted with heavy machine guns rumbled past the small African Union peacekeeping patrol as it struggled to pull the stranded cars from a sandy riverbed.

Inside the trucks, about 50 young Arab militiamen brandished weapons such as rocket-propelled grenade launchers and automatic rifles. As they rode past, the fighters — most of them appearing to be excitable teens with scarves masking their faces — shouted and shook their fists at the stranded peacekeepers.

Janjaweed militiamen are streaming into this northern part of Darfur to support Sudanese government troops battling rebels in a new and intense outbreak of fighting.

But local leaders say the militiamen also pose an increasing threat to ethnic African refugees, even within refugee camps that are near the bases of the 7,000-strong AU force.

Tribal leaders at Fata Borno said Janjaweed convoys have been passing by their camp here on a nearly daily basis, headed north from the Arab stronghold of Kebkabiya where their training camps are believed to be located.

Menacing as the Janjaweed convoys are, refugees said they are even more afraid of other armed Arab nomads in the area.

In general, international observers believe a toxic mix of both the Janjaweed and other Arab nomads, allegedly armed by Sudan's government, are responsible for many of the atrocities in Darfur.

Sudan's government is accused of raising and equipping the Janjaweed in 2003 to help put down an uprising by ethnic African villagers. The government has acknowledged using several paramilitary groups to reinforce its army in Darfur.

But the government blames atrocities on bandits that are beyond its control.

"These ... aren't the most dangerous ones," whispered 10-year-old refugee Najmaddin Idriss, huddling behind the African soldiers as the Janjaweed militiamen passed by in their pickup trucks.

"The ones over there are much more dangerous," he said, pointing to a spot down the riverbed where dozens of camels belonging to the other Arab fighters were grazing.

"The real danger comes from the (Arab) tribes who stay here," said refugee leader Ali Abubakar, and don't stream through periodically like the Janjaweed. "My people get killed, raped and looted all the time."

The other Arab nomads have long roamed the barren expanses of northern Darfur, he and others said. "They only became nasty at the beginning of the war, when the government gave them weapons," Abubakar said.

In the meantime, the presence of the African peacekeepers does little to relieve the terror. Fertile lands within a half mile of the Fata Borno camp are now off limits.

"Anyone who goes beyond that point is risking his life," Sheik Ibrahim Abdallah said, pointing at trees a few hundred yards away.

He said that some refugees tie their animals close to the African Union outpost alongside the camp.

"But even there, under the lights of the peacekeepers, donkeys get stolen," he said.

U.N. humanitarian chief Jan Egeland this week warned that the Janjaweed were becoming even more dangerous because of new equipment they were apparently receiving from the Sudanese government.

The militias "are more brutal than ever," Egeland told reporters in Geneva. "The nightmare we are seeing in Darfur is continuing."