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

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.