At least 87 people have been killed or are missing and 40 injured after intense Israeli airstrikes overnight in the north of the Gaza Strip, part of the country’s ferocious renewed assault on the area, medics in the besieged Palestinian territory have said.

In the past 24 hours 108 people had been killed in bombings across the territory, according to local health officials on Sunday. “The nightmare in Gaza is intensifying. Horrifying scenes are unfolding in the northern strip amidst relentless Israeli strikes and an ever-worsening humanitarian crisis,” Tor Wennesland, the UN special coordinator for the Middle East peace process, said in a statement

“Nowhere is safe in Gaza … We owe it to the families suffering in Gaza and Israel. The war must stop now,” he added

Bombings late on Saturday night in the town of Beit Lahiya flattened several houses and an apartment block, killing members of several families, according to Raheem Kheder, a medic. Among the dead were two parents and their four children, and a woman, her son and daughter-in-law and their four children, he said.

The internet and phone services have been down in parts of Gaza since Saturday evening, complicating the rescue operation.

In a post on X, Mounir al-Bursh, the director general of the health ministry, said the flood of injured people from the strikes compounded “an already catastrophic situation for the healthcare system” in northern Gaza.

There was no immediate comment on the strikes in Beit Lahiya from the Israeli military, which said it was “continuing to operate across Gaza in both aerial strikes and ground operations”.

The Israel Defense Forces (IDF) have nominally held complete control of northern Gaza since January, but launched a new assault on the area two weeks ago that they said was aimed at stopping Hamas militants from regrouping.

Gaza’s civil defence service said it had recovered at least 500 bodies since the operation began on 6 October

Sweeping evacuation orders for the estimated 400,000 people still living in the northern third of the territory, the blockage of aid and food deliveries and the targeting of civilian infrastructure such as hospitals have led rights groups to accuse Israel of the war crime of seeking to forcibly displace the remaining population.

Israel has denied it is systematically removing Palestinians from the area.

Several struggling hospitals have been unable to evacuate patients, and two people at the Indonesia hospital in Beit Lahiya died from a lack of oxygen after electricity and fuel shortages, the health ministry in the territory said.

The tightening of the siege on northern Gaza comes as Israel’s new war with Hezbollah in Lebanon deepens.

Israel said its air force attacked Hezbollah’s intelligence headquarters in Beirut on Sunday, as well as an underground workshop for the production of weapons, and killed three commanders. Hezbollah made no immediate comment.

Lebanon’s army, which has remained on the sidelines during the new war between Hezbollah and Israel, said three of its soldiers were killed by an Israeli strike while travelling in an army vehicle in the south of the country.

According to the IDF, Hezbollah fired 170 rockets into Israel on Sunday, with a resulting fire causing three minor casualties. Most of the projectiles were intercepted by Israel’s air defence systems.

On Sunday night hundreds of Beirut residents fled their homes after Israel said it was preparing attacks on sites linked to al-Qard al-Hassan, a Hezbollah-run banking system that provides loans and services primarily to people who live in areas where the militia group is popular.

Soon after the Israeli warning, several blasts were heard and a large fire was seen in Beirut’s southern suburbs.

The UN peacekeeping force in Lebanon (Unifil) said on Sunday evening that an Israeli army bulldozer had deliberately demolished an observation tower and perimeter fence at its position in Marwahin in southern Lebanon.

Unifil said in a statement: “Yet again, we remind the IDF and all actors of their obligations to ensure the safety and security of UN personnel and property and to respect the inviolability of UN premises at all times.”

Meanwhile, world powers are awaiting Israel’s retaliation against Iranian strikes on the Jewish state on 1 October that were launched in support of Tehran’s Lebanese ally.

Late on Friday, it emerged that top-secret US documents that allegedly reveal details about Israel’s plans to attack Iran had been leaked and published online.

Washington has not denied that the files, which appear to be the US’s assessment of Israel’s preparations, are authentic. The papers supposedly date from 15 and 16 October, and allege that Israel has fortified underground warplane bunkers at the Hatzerim airbase, where there are signs of preparation for arming plane-launched ballistic missiles

An Israeli source told the Israeli daily Haaretz that the US had apologised to Israel for the leak.

In an interview with CNN, the US House speaker, Mike Johnson, said on Sunday that an investigation into the incident had been launched.

Netanyahu has called a national security council meeting for Sunday evening in which it is expected that a response to Iran will be discussed. The US secretary of state, Antony Blinken, is scheduled to arrive in Israel on Tuesday to discuss Israel’s multifront war and a renewed international push for a ceasefire after the killing of the Hamas leader, Yahya Sinwar, in Rafah last week.

Israel and Hamas, however, have so far stuck to their irreconcilable demands. Internationally mediated talks aimed at a lasting truce in Gaza and the return of Israeli hostages kidnapped by Hamas during the 7 October attack that sparked the war broke down in August.