Hundreds of Palestinians on hunger strike in Israeli jails said on Friday they would shun vitamin supplements and prison clinics in an escalation of their mass protest against detention conditions.

"We swear we will not retreat. We are potential martyrs. Either we live in dignity or die," prisoner organizers said in a letter announcing the move and which was read out by Hamas's Ismail Haniyeh in the Gaza Strip, during a demonstration.

An estimated 1,600 inmates out of 4,800 launched the hunger strike on April 17 to demand improved conditions in Israeli custody, such as an end to solitary confinement and more family visits. They have also challenged Israel's policy of administrative detention without charge.

In the West Bank, weekly protests normally held against the West Bank barrier were held in solidarity with the hunger-strikers and for the upcoming Nakba Day.

In the Walaja village near Jerusalem, several hundred Palestinian protesters held a demonstration, marching toward the barrier and reaching a nearby spring. Activists reported that security forces were using tear gas and rubber bullets in an attempt to disperse the protesters. The IDF said some protesters threw stones.

In Jerusalem, several dozen protesters carrying signs, flags and pictures of prisoners marched from the Damascus Gate toward the Jerusalem Magistrate's Court. Police reported no disturbances.

Other protests took place in Hebron, Nablus, Kfar Kudoum, Nabi Saleh, Bil'in and Ramallah. Palestinians reported that an 18 year old was struck in the head with a projectile and seriously injured.

The fate of the hunger strikers has touched a raw nerve among Palestinians, with daily support rallies in the West Bank and Gaza, and political leaders warning that Israel could face new violence should any prisoner die.

Dozens of Palestinians, including from armed groups and politicians who had served terms in Israeli jails in the past, have gone on hunger strikes in tents put up in solidarity in the West Bank and Gaza Strip, which witnessed daily heavy attendence by residents and visitors from Arab and foreign countries.

The prisoners include Islamists from Hamas and Islamic Jihad, which reject peace with the Jewish state, as well as members of Fatah.

Jerusalem says all prisoners receive adequate medical attention, including in civilian hospitals if required.

An Israel Prisons Service spokeswoman said there was no immediate sign of the hunger strike being stepped up.

"As of now, I know that those who should be receiving extra care are receiving it," spokeswoman Sivan Weizman said.

In defense of administrative detention, Jerusalem says some cases cannot immediately be brought to open court for fear of exposing Palestinian intelligence sources that have cooperated with security services.

Two inmates who helped launch the hunger strike, Bilal Diab and Thaer Halahla of Islamic Jihad, were in the 74th day of their fast on Friday.

Anat Litvin of Physicians for Human Rights in Israel quoted Halahleh's doctor as saying his death could be imminent.

"What is very worrisome is the fact that he said that he doesn't want to be saved if something happens to him and he loses consciousness," Litvin said, adding that the IPS's medical facilities might prove inadequate.

"They don't have the equipment, they don't have the expertise; constant follow-up that is very much needed is not available," she told Reuters Television in Tel Aviv.

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