Hundreds of Palestinians in Israeli jails began a hunger strike on Monday in response to a call by prominent prisoner Marwan Barghouti, widely seen as a possible future Palestinian president.
Palestinians termed the open-ended strike a protest against poor conditions and an Israeli policy of detention without trial that has been applied against thousands since the 1980s.
Israel said the move by the prisoners, many of whom were convicted of attacks or planning attacks against Israel, was politically motivated.
The protest was led by Barghouti, 58, a leader of the mainstream Fatah movement of the Palestine Liberation Organization, serving five life terms after being convicted of murder in the killing of Israelis in a 2000-2005 uprising.
The strike, if sustained, could present a challenge to Israel and raise tensions between the two sides as the 50th anniversary of the Israeli occupation of the West Bank, East Jerusalem and the Gaza Strip approaches in June.
In an opinion piece in the New York Times on Monday, Barghouti said a strike was the only way to gain concessions after other options had failed. Almost 6,500 Palestinians are being held in 22 Israeli prisons.