Clashes between riot police and anti-government protesters in the Lebanese capital, Beirut, have left dozens of people wounded, witnesses say.
The violence began as demonstrators, who had been attacked during a sit-in by masked counter-protesters, tried to move into a square near parliament.
Police fired tear gas and rubber bullets, while protesters threw stones. At least 20 officers were also wounded.
Protests over economic mismanagement by the ruling elite began in October.
Saturday's events are some of the worst violence since the largely peaceful protests started. They triggered the resignation of the Prime Minister, Saad al-Hariri, but talks to form a new government are deadlocked.
"It was a very peaceful protest. Everyone was singing chants that we're one people, that we're all peaceful and then some of the young guys pushed one of the fences that separated us," Mona Fawaz, who was at the protest, told the BBC.
"We saw an enormous amount of police come out and really disperse us, push us and then they started [firing] tear gas on us. There was really no reason for all this demonstration of force."
Riot police and security forces had been deployed in large numbers in Beirut, chasing demonstrators, beating and detaining some of them, Reuters news agency reports.
Some protesters tried to push through steel barriers blocking the way to the parliament and government buildings. Clashes continued late into Saturday night.
The Lebanese Civil Defence said it had treated 54 people for injuries, taking more than half to hospital. It was not clear whether they were all civilians.
The protests have been the largest seen in Lebanon in more than a decade. They have cut across sectarian lines - a rare phenomenon since the devastating 1975-1990 civil war ended - and involved people from all sectors of society.
Demonstrators are angry at their leaders' failure to deal with a stagnant economy, rising prices, high unemployment, dire public services and corruption.
Their demands include an end to government corruption and the overhaul of the political system and the formation of an independent, non-sectarian cabinet.
Talks between President Michel Aoun and parliamentary blocs to name a new prime minister were expected to be held on Monday.