Friday's march targeted in particular Ansar al-Shariah, a militia of Islamic extremists who officials and witnesses say participated in the consulate attack. The group is also accused of attacking Muslims who don't follow its harsh interpretation of Islam.
"No, no, to militias," the giant crowd chanted as it marched along a lake in the center of Benghazi, 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?"
Other signs mourned the killing of U.S. Amb. Chris Stevens, reading, "The ambassador was Libya's friend" and "Libya lost a friend."
"Benghazi has been thrown wide open, it's full of chaos, looting and crime," said Ihsan Abdel-Baqi, a woman in her 50s who joined the march. "We want our dignity back. We are not afraid of anything."
The giant crowd poured into a square in front of the main camp of Ansar al-Shariah in the city, unfurling a long Libyan flag and chanting, "With our lives and souls, we redeem you, Benghazi." Military helicopters and fighter jets flew overhead, and police mingled in the crowd.
Several thousand Ansar al-Shariah supporters lined up in front of the camp in the face of the crowd, waving black and white banners. But there was no immediate friction between the two sides.
The militias first arose when Benghazi and the rest of the east rose up against Gadhafi's rule early last year. Residents formed local "brigades" that took up arms and fought regime forces. Over the civil war that followed such militias formed around the country.
Since Gadhafi's fall and death around a year ago, the militias have remained in place and have grown stronger, boasting arsenals of automatic weapons, rocket-propelled grenades and pick-up trucks with heavy machine guns. Many have no particular ideological bent, but some are strongly Islamist.
Their strength was on display in the Sept. 11 attack on the consulate. Heavily armed gunmen believed to be militiamen mixed in with a crowd of Libyans protesting an anti-Islam film outside the mission, Libyan officials say. Libyan security forces at the scene withdrew because they were heavily outnumbered and outgunned.
The government has been unable to convince militias to disband or integrate into the regular army or security forces, which remain underfunded and weak. Many say authorities have inadvertently fueled the growth with a program that pays militiamen to join a state-sponsored council that does little to bring them under government control.