At least 31 people have been killed and more than 200 wounded in Tripoli after militiamen opened fire on protesters who had marched to the headquarters of a militia to demand that it leave the Libyan capital.
The militias are holdovers from the 2011 uprising that ousted dictator Moammar Gadhafi and are a powerful force in the increasingly lawless North African country.
The protesters marched to the Gharghour neighborhood, home to the headquarters of a militia originally from the city of Misrata that has a powerful presence in Tripoli.
The demonstrators waved Libyan and white flags and chanted, "We want an army, we want police," referring to demands that the country's weak security forces take the place of militias.
At first the gunmen inside fired into the air to scare them off. But as the march continued, they started firing at the protesters.
Demonstrators fled but then returned, heavily armed, to attack the compound, where the militiamen remained holed up past nightfall.
The Reuters news agency reports dozens of soldiers tried to separate the two sides, and sealed off roads into Tripoli in an attempt to prevent more people joining the clashes.