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.

The leaders of France, Egypt and Jordan have warned Israel against a threatened offensive in the southern Gaza city of Rafah, urging an "immediate" ceasefire in its war on Hamas.

"We warn against the dangerous consequences of an Israeli offensive on Rafah, where more than 1.5 million Palestinian civilians have sought refuge," they said in a joint editorial published in several newspapers.

Turkey and Israel announced tit-for-tat trade barriers on Tuesday as relations between them further deteriorated amid the war in Gaza.

Turkey, a staunch critic of Israel's military actions in Gaza, first announced that it was restricting exports of 54 types of products to Israel with immediate effect. The products include aluminum, steel, construction products, jet fuel and chemical fertilizers. Responding to the Turkish trade restrictions, Israel said it was preparing a ban on products from Turkey.

Hamas said Tuesday it was considering a new truce framework proposed during the latest talks in Cairo, as Palestinians returning to their homes in southern Gaza confronted the extent of destruction left after Israeli troops' withdrawal.

Six months into the bloodiest Gaza war, Qatari, Egyptian and U.S. mediators have proposed another temporary ceasefire, according to a Hamas source.