The United States, which has been leading diplomatic efforts aimed at de-escalating the conflict across the Lebanese-Israeli border (but also has been arming Israel), has condemned it as a horrific attack but did not directly accuse Hezbollah.

The statement from the White House said US support for Israel’s security was iron-clad and that it would “continue to support efforts to end these terrible attacks along the Blue Line, which must be a top priority”. The Blue Line refers to the frontier between Lebanon and Israel, which the UN peacekeeping mission, known as Unifil, is responsible for monitoring.

UN special coordinator for Lebanon Jeanine Hennis-Plasschaert and Unifil force commander Lt. Gen. Aroldo Lázaro warned that further intensification of strikes “could ignite a wider conflagration that would engulf the entire region in a catastrophe beyond belief”. They urged maximum restraint from all sides, adding they were in contact with both Israel and Lebanon.

It has gone 10:30am in Gaza and Tel Aviv. This is our latest live blog on Israel’s war in Gaza and the wider Middle East crisis.

Israeli warplanes carried out attacks against Hezbollah in Lebanon over Saturday night in apparent retaliation for a rocket attack on the Golan Heights that killed 12 people, including children.

“Overnight, the IAF struck a series of Hezbollah terror targets both deep inside Lebanese territory and in southern Lebanon, including weapons caches and terrorist infrastructure in the areas of Chabriha, Borj El Chmali, and Beqaa, Kfarkela, Rab El Thalathine, Khiam, and Tayr Harfa,” the military said.

Israel’s foreign ministry said on Sunday that Hezbollah had “crossed all red lines” with the deadly strike on the football pitch in a remote town in the occupied Golan Heights, which came amid a day-long barrage of rocket fire from Lebanon.

“Saturday’s massacre constitutes the crossing of all red lines by Hezbollah. This is not an army fighting another army, rather it is a terrorist organisation deliberately shooting at civilians,” the ministry said in a statement.

The foreign ministry said “an Iranian rocket” caused the deaths of “our boys and girls”. “Hezbollah is the only terror organisation which has those (rockets) in its arsenal”, it said. “Israel will exercise its right and duty to act in self-defence and will respond to the massacre.”

Israel’s prime minister, Benjamin Netanyahu, had earlier vowed that Hezbollah would “pay a hefty price”. Mohammad Afif, a senior Hezbollah official, denied responsibility for the strike that hit Majdal Shams, speaking to Reuters. In a statement, the Iran-backed militant group said it had “absolutely nothing to do with the incident”, accusing hostile media outlets of “false allegations”.

Iran warned Israel on Sunday against what it called any “new adventure” in Lebanon, in a statement issued by foreign ministry spokesperson Nasser Kanaani.

In other news:

• The Golan Heights attack struck the predominantly Druze town of Majdal Shams in the mountainous region, close to the border with Syria. Israel has occupied the area since 1967, annexing it in 1981. Israel’s Magen David Adom emergency services said “large numbers” of ambulances were dispatched to the scene to treat the casualties, all aged between 10 and 20 years old. Video and imagery showed young casualties strewn across the grass, some wearing sports shirts.

• A wave of Israeli airstrikes targeting central and southern Gaza have killed at least 50 and injured an estimated 200 people, with one strike hitting a school where thousands were seeking shelter. Palestinian health ministry officials said that at least 30 people were killed in an airstrike on the Khadija school in Deir al-Balah in the central Gaza Strip, resulting in a wave of critical injuries.

• The Associated Press reported that people searched the ruined classrooms for remains, combing through the rubble to gather body parts. They added that close to the hospital, where those killed in the strike were taken, their reporters witnessed people fleeing as an ambulance drove in the opposite direction. Inside the ambulance, they said, lay a dead toddler as well as a body shrouded in a blanket.

• Hamas issued a statement condemning the Israeli airstrike that killed dozens of people after hitting the school in Deir Al-Balah on Saturday. Hamas said the “massacre at Khadija School is a crime that confirms the Israeli enemy’s estrangement from all human values ​​and its defiance of all laws of war”. Gaza’s civil defence agency said that the school was housing about 4,000 displaced people who had taken refuge there.

• The strike in Deir al-Balah was accompanied by further strikes on Khan Younis, after a week of deadly fighting in Gaza’s second city. Strikes in Khan Younis killed at least 23 people since the early morning and injured 89 according to Palestinian health officials, as civilians were forcibly displaced from the city for the fourth day. Gaza’s civil defence agency said that about 170 people had been killed and “hundreds wounded” during an Israeli offensive in the Khan Younis city area over several days.

• In Al-Bureij refugee camp, five Palestinians were killed earlier in an Israeli airstrike on a house, while four others were killed in another strike on a house in Rafah, near the border with Egypt, medics said.

• Israel’s military ordered residents from more parts of Khan Younis “to temporarily evacuate to the adjusted humanitarian area in al-Mawasi – the second such adjustment made to the safe zone within a week. Juliette Touma, the director of communications for the UN agency for Palestinian refugees (Unrwa) said: “Referring to the orders as evacuation orders don’t do any justice to what this means. These are forced displacement orders. What happens is when people have these orders, they have very little time to move.”

• The Khan Younis evacuation orders and “intensified hostilities” have “significantly destabilised aid operations”, the UN said, reporting “dire water, hygiene and sanitation conditions” in the Palestinian territory.

• Members of Israel’s rightwing government have hit back at Kamala Harris over her demands for an immediate ceasefire in Gaza after she met Benjamin Netanyahu during his US visit. An unnamed Israeli official accused Harris of endangering a potential deal to free Israeli and dual-national hostages in Gaza. “Hopefully the remarks Harris made in her press conference won’t be interpreted by Hamas as daylight between the US and Israel, thereby making a deal harder to secure,” the Israeli media reported the official as saying.

• CIA director William Burns will meet this weekend in Rome with his Israeli and Egyptian counterparts and Qatar’s prime minister for talks on a Gaza ceasefire and the release of hostages by Hamas, a source has told Reuters. The source said Burns would meet Qatari prime minister Sheikh Mohammed bin Abdulrahman Al Thani and the Egyptian and Israeli intelligence officials on Sunday.