RAMALLAH (Ma'an) -- The PA Ministry of Detainee Affairs said Wednesday that Israel has tightened procedures against prisoners on a mass hunger-strike launched a day earlier.

The ministry said in a statement that Israel's prison administration put detainees in solitary confinement without electricity. Prisoners in Ashkelon jail said detainees were threatened with transfer to a new section, and banned family visits.

Israeli Prison Service spokeswoman Sivan Weizman said 1,200 detainees were on continuous hunger strike, and all hunger-strikers have had privileges removed. They were moved to a special section of the prison but are not in isolation, she said.

The Palestinian Authority ministry says 1,600 prisoners joined the hunger-strike on Tuesday, Palestinian Prisoners Day.

International rights group Amnesty International said Tuesday it was troubled by reported punitive measures against the hunger-strikers.

"We remain very concerned about reports that detainees have been denied access to independent doctors, and that some have been punished because of their decision to go on hunger strike -- including by being placed in isolation, fined, or otherwise ill-treated by Israel Prison Services officers," Deputy Middle East and North Africa Director Ann Harrison said.

Meanwhile, the prisons ministry said detainees have appointed representatives in their dialogue with the prison administration.

The hunger strikers have a long list of complaints, including Israel's use of solitary confinement, the difficulty many having in securing family visits and the strip searches that are imposed on visitors.

Palestinians also denounce so-called administrative detention, whereby Israel can imprison suspects indefinitely, without ever informing them of the charges they face or presenting their lawyers with any evidence. Over 300 Palestinians are held without charge in Israel, including around 20 MPs.