Israel is holding 9,300 Palestinians in prisons and detention centres, including around 250 children and 75 women, the Palestinian Prisoner's Society said in a statement.
The PPS said that the number includes thousands of Palestinians detained from the Gaza Strip, where Israel has carried out a brutal military assault since October.
More than 3,400 of the total number of prisoners are held under 'administrative detention' - a procedure that allows Israeli authorities to hold alleged suspected for six months at a time, which can be extended indefinitely.
Israel says the procedure allows authorities to hold alleged suspects in a measure to "prevent attacks", while continuing to gather evidence.
Rights groups say such a system is abusive to Palestinian children, who are mostly arrested on suspicion of throwing stones.
Administrative detainees are often held on secret evidence that is barred from even the suspects' lawyers from viewing.
The issue of Palestinian prisoners has been a central part of the recent escalation between Israel and Hamas, with the Palestinian faction demanding that Israel release the detainees in exchange for Israeli captives held in Gaza.
In their amendments to the recent ceasefire plan forwarded by US President Joe Biden, Hamas demanded that prisoners be released according to their seniority. The group also demanded that Israel be prevented from re-arresting Palestinians after their release.
Earlier this week, the Palestinian Legislative Council called for international intervention to inspect Israeli detention centres following the recent release of several emaciated looking prisoners after prolonged periods in custody.
Among those freed were Aziz Dweik, the Speaker of the Palestinian Legislative Council, with activists heightening alarm over his health after photos of him surfaced appearing frail and gaunt.
