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.

A month-long sweep for Palestinian militants in the northern West Bank could continue for a year, Israel’s defense minister said, adding that residents who fled will be barred from returning and that a contested UN relief agency’s work there will be halted.

A weeks-long Israeli offensive has demolished houses and torn up vital infrastructure in the heavily built up townships, Palestinian authorities said.