RAMALLAH, West Bank (AP) — An activist says more than 1,500 Palestinian prisoners have launched an open-ended hunger strike to demand better conditions in Israeli prisons, including more contact with relatives, and an end to Israel's practice of detentions without trial.

The protest began Tuesday and was led by Marwan Barghouti, a prominent figure in President Mahmoud Abbas' Fatah movement. 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 Abbas.

Qadoura Fares, an advocate for prisoners' rights, says 6,500 Palestinians are currently held by Israel. Palestinians marked Tuesday as Prisoners' Day.

Fares says 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.