Palestinians clashed with Israeli soldiers on Friday at several demonstrations in the West Bank held to support a prisoner observing an intermittent hunger strike to protest his incarceration.

The Israeli military said about 500 Palestinians threw rocks and rolled burning tires at soldiers who responded with tear gas during the main rally outside Ofer Prison in the West Bank. The protesters called for the release of Samer Issawi, who has been on an on-again, off-again hunger strike for several months as he serves time for alleged terror activity.

Protests spread to several other West Bank flashpoints which turned violent as well. Palestinian medics said they treated dozens of people for tear gas inhalation and minor wounds sustained from rubber bullets. Two Israeli soldiers were lightly injured, the military said.

The prisoner issue is an emotional one for Palestinians after decades of conflict with Israel. Palestinians generally view them as heroes, regardless of the reason for their imprisonment — even when their crimes have involved killing civilians. Last year hundreds of Palestinian prisoners used hunger strikes to seek concessions from Israel.

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

Some prisoners, like Issawi, were released on condition of travel limits. Israeli Prison Service spokeswoman Sivan Weizman said he was arrested after he violated the terms of his release. She said he was arrested for "terror activity" and sentenced to 26 years, but released in the 2011 prisoner swap after serving only six years.

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

Issawi's sister, Shirin, said he has been on hunger strike for 206 days. She said he has only been drinking water since January. She said the prison takes her brother to an Israeli hospital for treatment.

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."

Mideast envoy Tony Blair issued a statement expressing concern for the prisoner's health. "This issue needs to be resolved quickly in order to avoid a tragic outcome which has the potential to destabilize the situation on the ground," he said.

Palestinian 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.

Last year, hundreds of Palestinian prisoners won multiple concessions from Israel after going on hunger strikes — some that lasted weeks.

Last week, a Gaza man who carried out the longest-ever hunger strike by a Palestinian prisoner returned home. Akram Rikhawi ended his 103-day hunger strike last July in exchange for Israel's pledged to release him five months earlier than his scheduled release in June.

Rikhawi, 40, served a nine-year sentence for transporting suicide bombers.