A senior Hamas official said Thursday that only a ceasefire can provide "enough time and safety" to locate Israeli hostages held across the Gaza Strip and ascertain their fate.

Negotiations for a ceasefire have been under way in Cairo since Sunday, but so far there has been no breakthrough on a proposal presented by U.S., Qatari and Egyptian mediators.

U.S. Secretary of State Antony Blinken has asked China's foreign minister and other counterparts to use their influence to dissuade Iran from striking Israel, the State Department said Thursday.

Blinken spoke by telephone over the past day to his Chinese, Turkish, Saudi and European counterparts "to make clear that escalation is not in anyone's interest and that countries should urge Iran not to escalate," State Department spokesman Matthew Miller told reporters.

Israel's Defense Minister Yoav Gallant has said it is planning to flood starving Gaza with aid through a new crossing and a port just north of the besieged territory.

With Israel under severe international pressure to allow more food in, Gallant said it planned to ramp up aid deliveries to 500 trucks a day -- the pre-war figure cited by the U.N.

Hamas chief Ismail Haniyeh insisted that the death of three of his sons in an Israeli air strike would not influence truce talks in Gaza, as bombardments on Thursday rocked the Palestinian territory.

Israel confirmed the killings, which came as talks in Cairo for a temporary ceasefire and hostage release deal drag on without signs of a breakthrough.

Israel was on alert Thursday after its arch foe Iran threatened reprisals over a strike in Syria this month that killed two Iranian generals, and as the war against Hamas ground on in Gaza.

Days after Israel strengthened its air defences and paused leave for combat units, the United States also warned of the risk of an attack by Iran or its allied groups at a time when Middle East tensions have soared.

Three sons and three grandchildren of Hamas' top political leader were killed Wednesday by an Israeli airstrike in the Gaza Strip, and the leader accused Israel of acting in "the spirit of revenge and murder."

U.S. President Joe Biden issued some of his sternest criticism yet of Israel's war on Hamas, calling its approach a "mistake" as the country faces a Wednesday court deadline to prove it is not throttling aid to hunger-stricken Gaza.

With global outrage over the toll inflicted by the six-month-old war growing, Biden rebuked Israeli Prime Minister Benjamin Netanyahu's handling of the conflict and reiterated the need for a ceasefire.

Spanish Prime Minister Pedro Sanchez warned Wednesday that Israel's "disproportionate response" in the Gaza war with Hamas risks "destabilizing the Middle East, and as a consequence, the entire world."

Iran's supreme leader Ayatollah Ali Khamenei again warned Israel Wednesday that it "will be punished" for a Damascus air strike that killed seven Revolutionary Guards, two of them generals.

"The evil regime made a mistake in this regard. It must be punished and will be punished," Khamenei said in a televised speech after Eid al-Adha prayers in Tehran.

Israeli warplanes struck a Syrian military position overnight in response to rocket fire on the Israeli-annexed Golan Heights, the military said on Tuesday.

The cross-border fire came days after an air strike blamed on Israel destroyed the Iranian consulate in Damascus, killing senior military commanders and raising regional tensions.