At least 1,350 Palestinian prisoners being held in Israeli jails are observing an open-ended hunger strike, the Israeli Prisons Service said on Sunday, after another 150 inmates began refusing food.

"There are now 1,350 Palestinian prisoners on hunger strike," said Sivan Weizman, spokeswoman for the Israel Prisons Service (IPS). "An additional 150 prisoners joined the hunger strike over the weekend, bringing the total number of prisoners on hunger strike to 1,350," she told AFP.

On Tuesday, 1,200 prisoners began an open-ended hunger strike to protest the conditions in which they are being held as Palestinians across the territories marked Prisoners´ Day, the IPS said. Another 2,300 prisoners also joined a day-long fast.

Before Tuesday´s mass protest, 10 Palestinian inmates of Israeli prisons were already on hunger strike, four of whom had been transferred to prison hospitals because of fragile health, the Palestinian Prisoners Club said.

Two of them, Bilal Diab, 27, and Thaer Halahla, 34, have now been refusing food for 54 days, with prisoner rights group Adameer describing their condition as "rapidly deteriorating."

All 10 are being held without charge under administrative detention orders, which means they can be held for renewable periods of up to six months.

There are 4,699 Palestinians being held in Israeli jails, of whom 319 are in administrative detention, according to Prisoners Club figures. (Copyright © 2012 Agence France Presse. 04/22/12)