Palestinian prisoners have launched one of the biggest hunger strikes in recent years in a protest against prison conditions.
As many as 1,500 prisoners could be participating in the strikes, which have been planned to coincide with the annual Palestinian Prisoners Day.
The strike also comes ahead of commemorations this summer marking 50 years since the 1967 Six Day War and the start of Israel's occupation of the Gaza Strip and West Bank.
The strike has been called for by prominent Palestinian prisoner and leader Marwan Barghouti, who is currently serving a life sentence over his role in the second Palestinian intifada - or uprising.
In an opinion piece written for the New York Times, the 57-year-old said: "Decades of experience have proved that Israel's inhumane system of colonial and military occupation aims to break the spirit of prisoners and the nation to which they belong, by inflicting suffering on their bodies, separating them from their families and communities, using humiliating measures to compel subjugation.
"In spite of such treatment, we will not surrender to it."
Issa Qaraqe, head of prisoners' affairs for the Palestinian Authority, said that "around 1,300 Palestinian prisoners" were participating in the hunger strike and the number could rise.
The Palestinian Prisoners Club non-governmental organisation put the number at 1,500.
The striking prisoners are demanding access to phones, extended visiting rights and better medical service.
Israeli public radio reported that Public Security Minister Gilad Erdan had described the demands as "unreasonable".
The challenge to the Israeli authorities comes at a time of reduced violence.
Some 6,500 Palestinians are currently detained by Israel for a range of offences and alleged crimes, and for many Palestinians the prisons themselves have become a stark symbol of Israel's occupation.
Of that number, 300 are minors and some 500 are held under administrative detention, which allows for imprisonment without charges or trial.
While hunger strikes by Palestinian prisoners are not uncommon, the scale of this movement is unusual.