KHARTOUM, Sudan — Turmoil in Darfur worsened yesterday when civilians assaulted African Union peacekeepers and the withdrawal of aid workers from the troubled area continued a day after at least 30 people were killed in ambushes.Most of the violence in the vast region nearly the size of Texas is blamed on the pro-government janjaweed militias, who ambushed and executed some 30 civilians on Saturday outside Sirba on a road near the border with Chad, United Nations and aid workers said yesterday.

The governor for West Darfur said the attack near Sirba wasn’t perpetrated by janjaweed but by rebels seeking “to make citizens loose confidence in the African Union.”

Aid workers in El Geneina, the capital of West Darfur, and the UN said the assailants were janjaweed on horseback who ambushed a truck and killed about 30 people. “Some of the passengers were shot by the attackers and others were burnt to death,” the UN said in a statement.

The spokesman for the 7,000-strong AU mission in Darfur, Noureddine Mezni, said a helicopter crew and team of AU peacekeepers sent yesterday to investigate the killing were detained for several hours by an angry mob of civilians in Sirba before being released.

Several hundred AU peacekeepers were also attacked in their base in El Geneina.

AU peacekeepers returned fire when they saw that assailants were armed with rocket-propelled grenades, an AU soldier said. It was not clear who the assailants were, said the soldier on condition of anonymity because he was not authorised to speak to the media.

In a sign of the AU’s difficulties in Darfur, Sudanese police were deployed around the camp to protect the peacekeepers.

The police presence suggested that the attack was by civilians frustrated with the AU, not by the janjaweed, said a UN official.

“There seems to be an alarming pattern of civilians assaulting the AU,” he said, speaking on condition of anonymity because of the sensitivity of the issue.

The incident in El-Geneina was the second time in a week that civilians turned on AU peacekeepers.

In the North Darfur capital of El-Fasher, civilians including refugees rioted, saying the peacekeepers should leave unless they do better protecting people against the janjaweed.

More than 200,000 people have been killed and 2.5 million have been forced from their homes since ethnic African rebels rose up against the Arab-dominated government in early 2003.

Khartoum is accused of responding by unleashing the janjaweed militias of Arab nomads, who are blamed for most of the atrocities.

The Sudanese government denies using the janjaweed and opposes replacing the AU force with a joint mission of some 20,000 UN and African peacekeepers.

An aid worker in El Fasher — where at least 10 people have been killed in janjaweed violence over the past week — said militia members in the town were dressed in government paramilitary uniforms.

Khartoum is accused of incorporating janjaweed into paramilitary units, but denies this saying that the soldiers are regular troops who do not commit war crimes. UN officials say these troops have killed hundreds of civilians in recent weeks.

A UN official in El Fasher said the governor of North Darfur had submitted his resignation to protest the janjaweed’s violence and how little control he had over the militia that the army had brought into town.

The UN official, who spoke on condition of anonymity because of the sensitivity of the issue, said at least one government security guard died Sunday after he was wounded earlier this week while protecting the governor’s compound that came under janjaweed fire.

“That the governor and his staff want to resign shows just how chaotic the situation has become,” warned Said Haroun, the spokesman for the Darfur rebel group that signed a peace deal with the government.

Authorities didn’t comment the governor’s reported resignation, but the official SUNA news agency said the Sudan’s police chief, defence and interior ministers had arrived in El Fasher to “review the situation.”

Some 160 UN staff and aid workers left North Darfur towns during the past week, and 41 aid workers have been withdrawn from various locations in South Darfur where an aid group’s compound was raided and vehicles stolen by armed men in uniform, the UN said.

The UN also said the army and militias had clashed with rebels in central Darfur, where two people were reported killed yesterday.

In the West Darfur camp of Zalingei, over 40 refugees were being held hostage by armed men on camels after three Arab nomads were mobbed in the camp.

An elderly refugee woman was also raped in retaliation, said an aid worker on condition of anonymity for fear of reprisals.

Small crowds gathered yesterday in various European and American cities to protest rapes and harassment in Darfur during the International Human Rights Day.