The US urged restraint on Israel as Washington and Saudi Arabia stepped up efforts to prevent the war with Hamas from spiralling into a regional conflict.

Secretary of state Antony Blinken called on Israel to take steps to avoid civilian casualties at a press conference on Thursday with Prime Minister Benjamin Netanyahu, whose newly formed unity government is preparing a ground invasion of the Gaza Strip.

Blinken also reiterated a warning to other regional actors not to “take advantage” of the crisis to attack Israel, amid concerns that a broader conflict could draw in Iranian-backed militant groups in Lebanon, Syria and elsewhere.

“Israel has the right, indeed the obligation, to defend itself and to ensure that this never happens again,” Blinken said, referring to the deadly incursion Hamas mounted from Gaza at the weekend, which killed more than 1,000 people, including 25 Americans.

But he added: “How Israel does this matters. We democracies distinguish ourselves from terrorists by striving for a different standard . . . That’s why it’s so important to take every possible precaution to avoid harming civilians.”

Netanyahu said: “Hamas is Isis and, just as Isis was crushed, so too will Hamas be crushed.” He added: “There will be many difficult days ahead, but I have no doubt that the forces of civilisation will win.”

The Israel Defense Forces said on Thursday they had dropped 6,000 bombs on more than 3,600 targets in Gaza so far.

Syrian state television also reported that Israel struck the country’s two main airports, in the capital Damascus and the northern city of Aleppo. The attacks were not immediately confirmed by the Israeli military.

Syrian air defences were launched in response to the attack, local media reported. The airports have been targeted several times this year.

Israel rarely acknowledges or discusses attacks it conducts in Syria. But it has carried out hundreds of strikes inside government-controlled regions in recent years — often targeting installations it says are tied to Iran’s Revolutionary Guards and allied militia groups.

Saudi Arabia’s Crown Prince Mohammed bin Salman also discussed the hostilities by phone with Iran’s president Ebrahim Raisi on Wednesday, in what Riyadh depicted as an effort to prevent the Israel-Hamas war from spreading.

It was the first such contact between the Middle East’s Sunni and Shia heavyweights for years.

Prince Mohammed, whose call with Raisi came after recent efforts to normalise relations with Israel, said the kingdom “was reaching out to all international and regional sides to end the current escalation”, according to the Saudi state news agency.

Raisi said Iran and Saudi Arabia, “as two key players [in the region], should defend the Muslim and oppressed nation of Palestine at this critical time”, according to a readout by Tehran.

Iran’s foreign minister Hossein Amirabdollahian was heading to the Iraqi capital Baghdad on Thursday to discuss issues including Gaza and is due to make a subsequent stop in Lebanon.

An Arab diplomat said Turkey, Egypt and Qatar were liaising with the Biden administration as they talk to Israel and the Palestinian militant faction. Doha, which hosts Hamas’s political office, is also focusing on convincing the group to release its dozens of hostages, hoping that would lead to a de-escalation.

Fears that the war with Hamas could spread into a second front with Hizbollah, the Iranian-backed Lebanese militant movement, on Israel’s northern border are a principal concern in Washington and elsewhere.

Before departing Washington, Blinken emphasised that the US had sent “the world’s largest aircraft carrier group to the region to make very clear our intent to deter anyone contemplating any further aggression against Israel”. In Israel, he added: “The US has Israel’s back.”

There have already been artillery exchanges across the Israel-Lebanon frontier, although both sides appear so far to be attempting to contain the hostilities.

Richard Hecht, a spokesperson for Israel’s military, said on Thursday morning that the country had deployed an additional division on the Lebanon border. He added that, although people were “very jumpy”, the situation in the north was “contained”.

Hecht said Israeli forces were still repelling sporadic attempts by Hamas militants to enter Israel from the sea, and were preparing for the next stage of the war. However, he said “no decision” had been taken on how it would be fought.

Israeli jets have been bombarding targets in Gaza since Saturday when the country was left reeling after Hamas militants launched the worst-ever attack on its territory. The assault killed at least 1,200 civilians and soldiers, and wounded more than 3,000, according to Israeli officials, who added that more than 5,000 rockets have been fired from Gaza.

Palestinian officials said on Thursday that 1,417 people had been killed by the Israeli strikes in Gaza, including 447 children and 248 women. They said 6,268 people had been wounded.

Tensions are also rising in the occupied West Bank, where authorities say 28 Palestinians have been killed in the past five days, and which Blinken is due to visit on Thursday, according to a senior Palestinian official.

Israel has cut off supplies of water, electricity, fuel and goods to Gaza, which Israel and Egypt have subjected to a crippling blockade since Hamas took control in 2007.

Palestinian officials said on Thursday that the territory’s health system had “begun to truly collapse” with intensive care beds completely filled.

The enclave’s only power plant ceased working on Wednesday and officials said medicine supplies were set to run out “imminently”.

The Egyptian government invited governments and organisations to send humanitarian aid for Gaza to al-Arish airport in the northern Sinai.

Cairo said the Rafah border crossing, the only entry point to Gaza that Israel does not control, was open, “contrary to inaccurate information that has been circulating”.

It said the crossing had not been closed at any point during the crisis but that Israeli air strikes targeting “basic infrastructure on the Palestinian side” had interrupted operations.

Israel Katz, Israel’s energy minister, posted on social media platform X, formerly known as Twitter, that until hostages were returned from Gaza, “no electrical switch will be turned on, no water hydrant will be opened and no fuel truck will enter” the enclave.

Israel’s military said more than 300 of its troops had been either killed or abducted into Gaza since Saturday’s incursion.

Additional reporting by Najmeh Bozorgmehr and Andrew England