Fierce clashes erupted in several places in the West Bank Friday between Israeli security forces and Palestinian protesters rallying in solidarity with hunger striking prisoners in Israeli jails, in what Palestinians said were the largest demonstrations in recent years.

At least 1,000 demonstrators massed outside Ofer prison, near Ramallah, and at least 200 Palestinians were injured in clashes with IDF soldiers, most of whom were treated for tear gas inhalation, according to the Palestinian Ma’an News Agency.

Two soldiers were lightly injured and received treatment on site, according to Channel 10.

The IDF Spokesperson said the soldiers responded to rocks thrown by protests with non-lethal crowd-dispersal methods.

Ma’an also reported that soldiers chased protesters in the hills surrounding the prison, and that the protesters managed to encircle a group of soldiers and pelt them with rocks. Additional soldiers broke through the ring of protesters and rescued the besieged troops.

Nearby, in the town of Beitunia, several hundred more Palestinians rioted and threw stone at soldiers, who responded with crowd-dispersal methods. At least nine Palestinians suffered injuries inflicted by rubber bullets fired by IDF soldiers, Israel Radio reported. One was moderately injured, and the IDF said it was investigating the circumstances of the man’s injury.

Additional protests took place in Hebron, Nablus, the Jalameh crossing near Jenin, Nabi Saleh, and the Qalandia crossing north of Jerusalem. Border Police officers stationed at Qalandia thwarted the advance of approximately 30 protesters who threw stones at the crossing.

The protesters held Friday prayers outside Ofer prison in support of Palestinian security detainees who have been on hunger strike for months. Samer Issawi has been on an on-off hunger strike for 198 days, and Tareq Qaadan and Jaafar Azzidine have refused food for 80 days, according to Ma’an.

Issawi, 35, was released in 2011 in a prisoner exchange: Israeli soldier Gilad Shalit was freed from Hamas captivity in Gaza in exchange for more than 1,000 Palestinian security prisoners, many of whom were convicted of being involved in suicide bombings and other deadly attacks.

Some prisoners in the deal, like Issawi, were released on condition of travel limits. Israeli Prison Service spokeswoman Sivan Weizman said he was rearrested after he violated the terms of his release. He had been convicted of “terror activity” and sentenced to 26 years, but had served only six years when first set free.

Issawi is under medical supervision and eats periodically, she said.

“If a hunger-striking prisoner dies the area will go up in flames and the occupation will be responsible for the consequences,” MK Ahmad Tibi (Ra’am Ta’al), who was at the Ofer Prison protest, cautioned.

Palestinian Authority President Mahmoud Abbas made an unannounced visit to a separate demonstration for prisoners near Ramallah. He said the prisoner issue would top his agenda in meetings with President Barack Obama, who is expected to visit the region next month.

The Palestinian minister of prisoner affairs, Issa Qaraqe, said Issawi began his fast in August and has been observing it intermittently.

Qaraqe said Issawi had lost 35 kilograms (about 77 pounds), has kidney pain and has lost feeling in parts of the right side of his body.

He said there are four prisoners on hunger strike.

Human rights groups have warned of their worsening health.

“If, God forbid, any prisoner dies of hunger strike inside the prison, the situation on the ground will deteriorate,” Qaraqe said. “People won’t stand for any prisoner to die of a hunger strike.”