Israel must free all Palestinians held without charges under so called "administrative detention" orders or give them a swift and fair trial, rights group Amnesty International said on Wednesday.
"Release all administrative detainees unless they are promptly charged with internationally recognisable criminal offences and tried in accordance with international fair trial standards," it said in a new report.
"End the practise of administrative detention," it added.
Administrative detention is a procedure dating back to the pre-1948 British Mandate under which military courts can hold suspects without charge for periods of up to six months, which can be renewed indefinitely.
Palestinian prisoners in Israeli custody ended a mass hunger strike on May 14, in return for improved conditions and an Israeli pledge that prisoners held without charge would be freed at the end of their current period of detention -- unless fresh evidence emerged against them.
But Palestinian prisoners minister Issa Qaraqaa said on Sunday that Israel was not keeping its end of the bargain.
"Israel has begun to violate the deal it signed with the prisoners, and within 10 days after announcing the end of the strike, Israel renewed administrative detention orders for approximately 30 prisoners," Qaraqaa said at a press conference.
One of the prisoners, Thaer Halahla who fasted for 76 days in the protest, was released on Tuesday evening, relatives said.
Family members in the West Bank city of Hebron said that Halahla, who along with fellow inmate Bilal Diab set a record for a Palestinian hunger strike, was freed after being held without charge since June 2010.
In its report,"Starved of justice: Palestinians detained without trial by Israel" Amnesty said that at the end of April there were at least 308 Palestinian administrative detainees.
"Among them 24 members of the Palestinian Legislative Council (PLC), including its speaker, Aziz Dweik, human rights defenders such as Walid Hanatsheh and at least four journalists, in addition to university students and academic staff."
Among its recommendations were that Israel end the forcible transfer of Palestinians from the West Bank to the Gaza Strip and that authorities "protect all those in Israeli custody from all forms of torture and other ill-treatment."