JANZOUR, Libya — When the sun sets on the refugee camp for black Africans that has sprung up at the marina in this town six miles west of Tripoli, the women here brace for the worst.

The rebels who ring the camp suddenly open fire. Then they race into the camp, shouting "gabbour, gabbour" — Arabic for whore — and haul away young women, residents say.

"You should be here in the evening, when they come in firing their guns and taking people," one woman from Nigeria said Wednesday as she recounted the nightly raids on the camp. "They don't use condoms, they use whatever they can find," she said, pointing to a discarded plastic bag in a pile of trash.

As she spoke, other women standing nearby nodded in agreement.

There is no way to know how many women have been raped here, where hundreds of Africans have settled in and around the boats of a marina. No one keeps statistics in the camp, and foreign aid workers say they are prohibited from discussing the allegations on the record. International Red Cross representatives say only that they have spoken to rebel leaders about "security concerns."

But the story that women tell is part of a larger picture of abuse of black Africans in Libya that is emerging in the wake of the rebel victory, born of allegations that Gadhafi often hired sub-Saharan Africans to fight for him.

Hundreds of black Africans have been swept up and are being held in makeshift prisons awaiting some sort of judicial finding of whether they were mercenaries or not. Thousands more are trapped in refugee camps. They can't leave the camps, they say, for fear they'll be targeted on the streets. They do not feel safe inside the camps, either.

Human rights advocates have decried what appears to be mistreatment of black African workers, and U.S. Ambassador Gene Cretz, speaking in Washington on Wednesday, admitted it's a growing problem.

"We've seen fairly credible reports that there has been some mistreatment of African migrants," Cretz told McClatchy. He said the U.S. was trying to work with rebel leaders to prevent abuse, which he blamed on young rebels who are confusing Africans who might have fought as mercenaries for Gadhafi with the hundreds of thousands of sub-Saharan Africans who were working in Libya when the rebels took over.

"We don't think it's a systematic or intentional problem on the part of the Libyan authorities," Cretz said. "It's something that's happening at levels below that, which is of considerable concern to us."

Cretz said the rebels' National Transitional Council is working with the United Nations and other international relief organizations to ease the situation.

There was little evidence of such efforts at the marina here, however. At the nearby headquarters of the revolutionary forces in the area, Mohammed Abdullah Fatouri, the head of the military council, said that he was unaware of any problems in the camp.

"Have them bring a letter," he said. "If they tell us this is happening, we will protect them."

At the camp itself, fear is pervasive. When a car bearing two armed rebels drove into the camp, both men and women scattered.

It was not clear what the rebels wanted. Someone said they were looking for laborers. Perhaps emboldened by a pair of European TV camera crews, however, some of the camp's residents confronted the rebels. An older man, apparently the translator for one of the European TV crews, intervened, and after a few minutes, the militiamen got back in the car and drove off.