A United Nations office said on Friday it was “seriously concerned” about a dramatic rise in Israel’s arrest of Palestinians and called for an investigation into allegations of torture in Israeli custody.

Israel has arrested more than 3,000 Palestinians in the occupied West Bank, including East Jerusalem, since the start of the Gaza war in early October and a record high number were being held without charge or trial, said a statement by the UN Human Rights Office in the occupied Palestinian territories.

Within the span of two months, six Palestinian men have died in Israeli custody, the highest number of cases in such a short period in decades, it said.

Since the October 7 Hamas attack and Israel’s subsequent heavy bombardment of Gaza, Palestinians held in Israeli jails have reported deteriorating conditions, including overcrowding, restricted access to food and water and limited visits from family or lawyers. Many have said they were subjected to beatings and abuse by detention guards, including rape threats.

“The massive rise in number of Palestinians arrested and detained, the number of reports of ill-treatment and humiliation suffered by those in custody, and the reported failure to adhere to basic due process raise serious questions about Israel’s compliance with international humanitarian law and international human rights law,” the UN Human Rights Office said.

“All cases of deaths in custody and allegations of torture and other ill-treatment must be investigated and accountability ensured.”

Israel’s Prison Service has said that all prisoners in its custody “are detained according to the provisions of the law” and that prisoners deaths were under investigation.

As part of a truce deal with the Palestinian group Hamas, which controls Gaza, Israel has released 240 Palestinian women and teenagers from its jails. More than half were detained without charge, according to Israel’s records.

During the week-long pause in fighting, Israel arrested more than 260 Palestinians in the occupied West Bank, the Palestinian Prisoners Society said.