A Palestinian Authority official, Issa Qaraqe, said Monday that "around 1,300 Palestinian prisoners" were participating in the hunger strike.

The NGO Palestinian Prisoners' Club said 1,500 people were taking part. The Israeli prison service on Monday put that number at about 1,100.

The hunger-striking prisoners were calling for better conditions including access to phones, better medical services and extended visiting rights for their families.

The Palestinian observer mission to the United Nations on Monday called for Israel to release thousands of Palestinians it said were "illegally and inhumanely" imprisoned and detained.

About 6,500 Palestinians are currently detained by Israel on a wide range of offenses and alleged crimes. According to Palestinian authorities and the advocacy group Addameer, some 500 of them are held under administrative detention which means they are jailed without charge or trial for a period of six months, which can be extended.

Israeli authorities argue administrative detention protects at-risk informants and is needed for the country's security.

Prominent prisoner called for hunger strike

A prominent leader in the Fatah party of Palestinian President Mahmoud Abbas, Marwan Barghouti, had called for the strike. Barghouti is serving multiple life sentences for murder for his role in the deadly uprising of the second Palestinian intifada in the early 2000s. Recent polls have shown the popular Fatah figure could win an election for the Palestinian presidency.

In an opinion piece published in "The New York Times," to coincide with the beginning of the hunger strike, Barghouti accused Israel of breaching international law when it came to the treatment of Palestinian prisoners.

"The Israeli authorities and its prison service have turned basic rights that should be guaranteed under international law - including those painfully secured through previous hunger strikes - into privileges they decide to grant us or deprive us of," he wrote.

Hana Herbst, a spokeswoman for the Israel Prison Service, said in a statement that striking prisoners were being transfered to separate cell blocks. Barghouti was put into solitary confinement

On Tuesday, Israeli Public Security Minister Gilad Erdan said there would be no negotiations with prisoners.

"They are terrorists and incarcerated murderers who are getting what they deserve and we have no reason to negotiate with them," Erdan told army radio.

Barghouti was put into solitary confinement for "instigating mutiny and leading the hunger strike," Erdan said.

To mark this year's prisoners' day, several rallies and other events were planned by Palestinian authorities in the occupied West Bank and the Gaza Strip.

cw/se/jm (dpa, AFP, AP)