Israeli bulldozers have demolished large areas of the now virtually empty Jenin refugee camp and appear to be carving wide roadways through its once-crowded warren of alleyways, echoing tactics already employed in Gaza as troops prepare for a long-term stay.

Gaza Hamas says it is delaying further negotiations with Israel until 620 Palestinian detainees, who were supposed to be released on Saturday, are handed over, placing the fragile Gaza ceasefire in jeopardy as violence escalates in the occupied West Bank.

Israeli tanks moved into the occupied West Bank on Sunday for the first time in decades in what Palestinian authorities called a “dangerous escalation,” after the defense minister said troops will remain in parts of the territory for a year and tens of thousands of Palestinians who have fled cannot return.

Israel has delayed an expected release of hundreds of Palestinian prisoners and detainees in exchange for returned Israeli hostages “until further notice,” the Palestinian Prisoners Society said early Sunday.

Israeli Prime Minister Benjamin Netanyahu’s office said that the release of Palestinian prisoners would be delayed until the next hostage release was assured.

Hamas will not hold talks with Israel through mediators on any further steps in the fragile, phased ceasefire agreement unless Palestinian prisoners are released as agreed, group official Basem Naim told Reuters on Sunday.