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.

Israel’s military sent tanks into the occupied West Bank for the first time in more than two decades as it expanded operations in the territory on Sunday in a move decried by Palestinian authorities as an escalation of aggression.