Hundreds of protesters angry over last week's killing of the U.S. ambassador to Libya stormed the compound of the Islamic extremist militia suspected in the attack, evicting militiamen and setting fire to their building Friday.

In an unprecedented show of public anger at Libya's rampant militias, the crowd overwhelmed the compound of the Ansar al-Shariah Brigade in the centre of the eastern city of Benghazi.

Ansar al-Shariah fighters initially fired in the air to disperse the crowd, but eventually abandoned the site with their weapons and vehicles after it was overrun by waves of protesters shouting "No to militias."

"I don't want to see armed men wearing Afghani-style clothes stopping me in the street to give me orders, I only want to see people in uniform," said Omar Mohammed, a university student who took part in the takeover of the site, which protesters said was done in support of the army and police.

For many Libyans, the Sept. 11 attack on the U.S. Consulate in Benghazi was the last straw in one of the biggest problems Libya has faced since the ouster and death of longtime dictator Moammar Gadhafi around a year ago — the multiple mini-armies that, with their arsenals of machine-guns and rocket-propelled grenades, are stronger than the regular armed forces and police.

The militias, a legacy of the rag-tag popular forces that fought Gadhafi's regime, tout themselves as protectors of Libya's revolution, providing security where police cannot. But many say they act like gangs, detaining and intimidating rivals and carrying out killings.

Militias made up of Islamic radicals like Ansar al-Shariah are notorious for attacks on Muslims who don't abide by their hardline ideology. Officials and witnesses say fighters from Ansar al-Shariah led the attack on the U.S. consulate, which killed Amb. Chris Stevens and three other Americans.

After taking over the Ansar compound, protesters then drove to attack the Benghazi headquarters of another Islamist militia, Rafallah Sahati. The militiamen opened fire on the protesters, who were largely unarmed. At least 20 were wounded, and there were unconfirmed witness reports of three protesters killed.

Earlier in the day, some 30,000 people filled a broad boulevard as they marched along a lake in central Benghazi on Friday to the gates of the headquarters of Ansar al-Shariah.

"No, no, to militias," the crowd chanted, filling a broad boulevard. They carried banners and signs demanding that militias disband and that the government build up police to take their place in keeping security. "Benghazi is in a trap," signs read. "Where is the army, where is the police?"

'Libya lost a friend'

Other signs mourned the killing of Stevens, reading, "The ambassador was Libya's friend" and "Libya lost a friend." Military helicopters and fighter jets flew overhead, and police mingled in the crowd, buoyed by the support of the protesters.

The march was the biggest seen in Benghazi, Libya's second largest city and home to 1 million people, since the fall of Gadhafi in August 2011. The public backlash comes in part in frustration with the interim government, which has been unable to rein in the armed factions. Many say that officials' attempts to co-opt fighters by paying them have only fueled the growth of militias without bringing them under state control or integrating them into the regular forces.

Residents of another main eastern city, Darna, have also begun to stand up against Ansar al-Shariah and other militias.

The anti-militia fervour in Darna is notable because the city, in the mountains along the Mediterranean coast north of Benghazi, has long had a reputation as a stronghold for Islamic extremists. During the Gadhafi era, it was the hotbed of a deadly Islamist insurgency against his regime. A significant number of the Libyan jihadists who travelled to Afghanistan and Iraq during recent wars came from Darna. During the revolt against him last year, Gadhafi's regime warned that Darna would declare itself an Islamic Emirate and ally itself with al-Qaeda.