Clashes between demonstrators in support of Palestinian prisoners held in Israeli jails and Palestinian Authority police left 18 people injured in the al-Amari refugee camp near the West Bank town of Ramallah on Sunday night.

The demonstration was proceeding peacefully until a group of youths began burning tires and blocked the main road of the camp. PA security forces came to the scene but were greeted with a hail of rocks and debris that injured 15 officers, Ynet reported.

After firing warning shots into the air, the security forces reportedly used live fire to disperse the protest, injuring three protesters, some of whom required hospitalization. They then made several arrests and cordoned off the camp.

The past few months have seen a rise in the number of clashes between the President Mahmoud Abbas’s PA and Abbas’s opponents in the West Bank.

Last week, Palestinian security forces in a refugee camp near Nablus failed to arrest two armed Fatah party members who had appeared, masked and armed, in an Israeli news item.

The PA security forces arrived at the Balata Refugee Camp in the early Thursday morning to arrest Mohammed Abu-Zu’bul and Iyad Tirawi, leaders in Fatah’s al-Aqsa Martyr’s Brigades, who had been caught on camera by Israel’s Channel 2 TV station parading their weapons around the camp and firing into the air.

The men were protesting ill treatment by the PA.

The Palestinian Authority is facing mounting criticism over its inability to pay civil servants’ salaries, which it blames on an unprecedented budgetary deficit.

Abbas’s popularity on the Palestinian street has plummeted in comparison to that of Hamas Prime Minister Ismail Haniyeh and imprisoned Fatah rival Marwan Barghouti, following Israel’s Operation Pillar of Defense in the Gaza Strip, according to a poll conducted in December.

Elhanan Miller contributed to this report.