Israel has claimed it killed Hezbollah’s top military commander, Fuad Shukur, in an airstrike on a south Beirut suburb launched in retaliation for a rocket attack that killed 12 children at the weekend. Shukur, also known as Hajj Mohsin, served as right hand man to Hezbollah leader Hassan Nasrallah, Israel’s military spokesperson R Adm Daniel Hagari said in a late night briefing. “The IDF will not tolerate terrorist attacks on Israeli civilians. We have been responding to these attacks with precise strikes on Hezbollah commanders, terror operatives and military infrastructure in Lebanon,” Hagari said. An adviser for planning and directing wartime operations, Shukur was responsible for most of Hezbollah’s advanced weaponry, including precise-guided missiles, cruise missiles, anti-ship missiles, long-range rockets, and UAVs, Israel said. He also had a $5m (£3.9m) bounty on his head in America over his role in the 1983 bombing of a US marine barracks in the Lebanese capital. Lebanon’s foreign minister said the strike in Beirut was a shock, after assurances from Israel’s allies that the country was planning a “limited response” that “would not produce a war”. “That’s what we’re afraid of, and hopefully this will not produce a war,” Abdallah Bou Habib told the Guardian. “We did not expect to be hit in Beirut. We thought these were red lines that the Israelis would respect.” Lebanon plans to file a complaint with the UN security council and ask Hezbollah “to have a proportional retaliation”, he added. “We want this cycle of destruction of killing and death to stop.” In his briefing, Hagari said: “Hezbollah’s ongoing aggression and brutal attacks are dragging the people of Lebanon and the entire Middle East into a wider escalation. While we prefer to resolve hostilities without a wider war, the IDF is fully prepared for any scenario.” The attack, just after sunset on Tuesday, hit a block of flats in Haret Hreik, a suburb known as a Hezbollah stronghold, causing a blast heard across the city. Three people, including two children, were killed and 74 people injured in the attack, the Lebanese ministry of health said in a statement. Hezbollah did not comment on the Israeli claims that Shukur had been killed. The top three floors of the building collapsed, and rescuers on cranes concentrated their efforts on clearing debris into the night. “There might still be people trapped under the rubble,” said Ali Abbas, one of the first responders. Shattered glass injured many people in surrounding buildings, including a nearby hospital, he added. Lebanon’s cabinet will hold an emergency session tomorrow morning to discuss the attack, which the caretaker prime minister, Najib Mikati, condemned as a “criminal act”. “The Israeli killing machine has not been satisfied by targeting the south of Lebanon and the Bekaa, it has now reached the heart of the capital Beirut, just meters away from one of the largest hospitals in Lebanon,” he said in a statement. Beirut had been bracing for Israel’s response to a rocket strike on a children’s football match in the occupied Golan Heights three days earlier. Israel and the US have blamed Hezbollah for the attack. Hezbollah has denied responsibility. The US had been leading a global diplomatic effort to deter Israel from hitting Beirut or Lebanese infrastructure, in an attempt to prevent escalation into full blown regional conflict. In a post on X after the strike, the Israeli defence minister, Yoav Gallant, said: “Hezbollah crossed the red line.” The mayor of the northern city of Haifa, Yona Yahav, sent a message to residents saying the city was “prepared for any scenario and are in close contact with the security forces”, and urging them to look out for announcements from authorities. The White House spokesperson Karine Jean-Pierre said soon afterwards that the US does not believe war between Hezbollah and Israel is inevitable, echoing earlier comments by the US defence secretary, Lloyd Austin. In Beirut, people were not so certain. As plumes of smoke billowed into the sky above the partly collapsed block of flats, anxious neighbours scrambled to leave the neighbourhood, fearful of further Israeli strikes. “This area is not safe any more, I expect there to be more. We might go to the mountains, it will be better for us,” Mira Slim, a 20-year-old university student living near the site of the airstrike, said through tears. Queues also formed at petrol stations across the city as people filled up their cars, wary of further escalation. Israel assassinated a top Hamas official, Saleh al-Arouri, with an airstrike on Beirut in January. Before that, Israeli forces had last targeted the city during the 34-day war between Israel and Hezbollah in the summer of 2006, when bombing raids largely flattened the same Harek Hreik neighbourhood that was struck on Tuesday. Russia swiftly condemned the attack as a violation of international law. Iran, Hezbollah’s main backer, condemned it as “sinful and cowardly aggression”. The Israeli prime minister, Benjamin Netanyahu, had vowed a “harsh” response for the attack in the town of Majdal Shams in the Golan Heights. A military statement described it as a direct response. “The IDF carried out a targeted strike in Beirut, on the commander responsible for the murder of the children in Majdal Shams and the killing of numerous additional Israeli civilians,” the Israeli military said. In their choice of target, however, Israel may have aimed to send a broader message to Hezbollah that it could reach the group’s leadership in its strongholds. Shukur is a member of the Jihad council, the group’s top military body. He is said to be in his early 60s and from Baalbek in eastern Lebanon. He has been involved in Hezbollah campaigns that spanning the Israeli invasion of Lebanon in 1982, Hezbollah’s intervention in the Syrian civil war in the 2010s and the tit-for-tat strikes with Israel of the past 10 months. “This is a serious strike and it does pose a real dilemma for Hezbollah and there’s a real question now about what they do,” said Michael Hanna, the US programme director at Crisis Group. “And then, of course, you are in the potential escalatory cycle, and headed down a path that ends up being not manageable, despite the broader aversion on both sides to all-out war.” Earlier on Tuesday, countries including the UK, Germany, France and America had urged citizens to leave Lebanon or avoid travelling there. The British foreign secretary, David Lammy, said on Tuesday morning that events were “fast-moving” and that British nationals were advised “to leave Lebanon and not to travel to the country”. Many airlines had cancelled flights to Beirut. Greece’s Aegean Airlines and Germany’s Condor were the latest to suspend services, joining others including Royal Jordanian, Air France and Lufthansa.