A large group of protesters tried to march to parliament on Dec. 14 where talks about establishing a new government are to begin on Dec. 16.
But security forces used tear gas to block demonstrators trying to cross barriers after they gathered in Martyrs Square.
Protesters pelted police with stones as clashes continued until late and dozens were injured on both sides.
Police said 20 officers were taken to the hospital and others were treated at the scene.
The Lebanon Civil Defense Units said more than 50 protesters were treated and 36 sent to hospitals.
Security forces have taken measures since Oct. 17 when anti-government protests began.
Lebanon has been rocked by mass protests in recent months against plans for tax increases, which quickly turned into wider grievances.
The unrest forced Prime Minister Saad Hariri to resign Oct. 29, with no progress on reaching a deal on a new government.
Hurriyet Daily News