Palestinian Authority policemen clashed Sunday night with hundreds of protesters in the Al-Amari refugee camp at the southern entrance to Ramallah.
At least 23 protesters and 15 policemen were injured, three of them seriously, during the clashes, Palestinians said.
The confrontation erupted when PA policemen tried to prevent demonstrators from blocking the main entrance to the camp, eyewitnesses said.
The demonstration was held in solidarity with Palestinians held in Israeli prisons, they added.
Policemen and security officers used gas tears and live ammunition to disperse the protesters, according to the eyewitnesses.
Other reports said that policemen and masked gunmen exchanged gunfire during the confrontation.
The PA declared the camp a "closed military zone" and prevented journalists from entering.
Residents said that the PA security forces arrested scores of young men on suspicion of participating in the demonstration.
A spokesman for the PA police in Ramallah accused the protesters of throwing stones and empty bottles at members of the security forces who arrived at the scene to enforce law and order.