More than 1,500 Palestinian prisoners have launched an open-ended hunger strike to demand better conditions in Israeli prisons.
Their demands include more contact with relatives and an end to Israel’s practice of detentions without trial, an activist said.
The protest began on Monday and was led by Marwan Barghouti, a prominent figure in the Fatah movement of President Mahmoud Abbas.
Opinion polls suggest Barghouti, who is serving multiple life terms for his role in a violent Palestinian uprising against Israeli occupation, is the top contender to succeed Mr Abbas.
Qadoura Fares, an advocate for prisoners’ rights, said 6,500 Palestinians are currently held by Israel. Palestinians marked Monday as Prisoners’ Day.
Mr Fares said hundreds of prisoners launched a 28-day strike in 2012. In 2014, dozens of detainees held without trial went on hunger strike for two months.
In the West Bank and Gaza, thousands staged solidarity marches to mark Prisoners’ Day in the Palestinian areas.
Barghouti wrote that Israeli prisons have become the “cradle of a lasting movement for Palestinian self-determination”.
“This new hunger strike will demonstrate once more that the prisoners’ movement is the compass that guides our struggle, the struggle for Freedom and Dignity, the name we have chosen for this new step in our long walk to freedom,” he wrote.
The hunger strike was launched as the approaching half-century milestone of Israeli rule over Palestinians appeared to generate new interest in the long-running conflict, which in recent years was often overshadowed by war and turmoil elsewhere in the region.
Israel captured the West Bank, Gaza Strip and east Jerusalem in the June 1967 war.
Mr Abbas and his supporters seek a Palestinian state, roughly in the pre-1967 lines.
The Islamic militant group Hamas, which seized Gaza from Mr Abbas in 2007, has called for an Islamic state in all of historic Palestine, including in what is now Israel.
Hamas recently suggested it would support a smaller Palestine state, without specifying if this would be a stepping stone to Israel’s destruction.
In Gaza City, about 2,000 people turned out for a march, raising flags of different Palestinian factions.
Militants from Hamas surrounded cages on trucks depicting cells.
One cage held two Palestinians in Israeli prison uniform. The other cage bore the pictures of two Israeli soldiers killed in the 2014 war between Israel and Hamas, and the pictures of two Israeli civilians who disappeared after entering Gaza.
Hamas is believed to hold the two civilians and the remains of the soldiers. “Your soldiers will not see the light unless the price is paid,” read a banner on the truck.
Ismail Radwan, a Hamas official who participated in the march, reiterated Hamas’ demand for a prisoner swap with Israel. In 2011, Israel swapped more than 1,000 Palestinian prisoners for an Israeli soldier who had been held by Hamas for five years.
In the West Bank town of Ramallah, Barghouti’s wife, Fadwa, joined about 1,500 marchers.
“This massive strike sends a strong message to the Israelis, after 50 years of occupation, suppression and oppression, that the prisoners… will lead their people from behind bars,” she said.