21 Israeli troops are killed in the deadliest attack on the military since the Gaza offensive began

JERUSALEM — Palestinian militants carried out the deadliest single attack on Israeli forces in Gaza since the Hamas raid that triggered the war, killing 21 soldiers, the military said Tuesday, a significant setback that could add to mounting calls for a cease-fire.

Hours later, the military announced that ground forces had encircled the southern city of Khan Younis, Gaza’s second largest, and thick, black smoke could be seen rising over the city as thousands of Palestinians fled south. Witnesses said Israeli tanks and troops had also moved into Muwasi, a nearby coastal area that the military had previously declared a safe zone for Palestinians.

Prime Minister Benjamin Netanyahu mourned the Israeli soldiers, who died when the blast from a rocket-propelled grenade triggered explosives they were laying to blow up buildings. But he vowed to press ahead until “absolute victory,” including crushing Hamas and freeing more than 100 Israeli hostages still held by the militants.

Israelis are increasingly questioning whether it’s possible to achieve those war aims.

A senior Egyptian official said Israel has proposed a two-month cease-fire in which the hostages would be freed in exchange for the release of Palestinians imprisoned by Israel and top Hamas leaders in Gaza would be allowed to relocate to other countries.

The official, who was not authorized to brief media and spoke on condition of anonymity, said Hamas rejected the proposal and insists no more hostages will be released until Israel ends its offensive and withdraws from Gaza. Israel’s government declined to comment on the talks.

Egypt and Qatar were developing a multistage proposal to try to bridge the gaps, the official said.