An Israeli airstrike hit a hospital in southern Gaza on Sunday night, leaving a part of the hospital in flames and causing multiple casualties, two doctors working at Nasser Medical Complex told CNN,

The United Nations is withdrawing about one-third of its international work force in Gaza, with the reduction coming after an Israeli tank shell hit a U.N. compound.

Israel previously threatened Gaza with "complete destruction and devastation"​ if Hamas didn't hand over the remaining hostages.

U.S. immigration authorities have detained and revoked the visa of a Turkish doctoral student at Tufts University near Boston who had voiced support for Palestinians in Israel's war in Gaza.

Israel has vowed to escalate the offensive if Hamas does not release hostages, disarm and leave the territory.

The Palestinian Health Ministry in Gaza said Wednesday the bodies of 39 people killed by Israeli strikes have been brought to hospitals over the past 24 hours. Hospitals also received 124 wounded, the ministry said in its daily report.

The United Nations has said it will “reduce its footprint” in the Gaza Strip after an Israeli tank strike hit one of its compounds last week, killing one staffer and wounding five others.

The strikes mark the most significant escalation in Israeli military action in the Gaza Strip since Israel and the militant group Hamas reached a tenuous ceasefire agreement nearly two months ago. Hamas has accused Israel of violating the fragile truce hundreds of times since it went into effect in January.