Iran’s supreme national security council has decided on a “required” response to the Israeli strike on Damascus on Monday night that killed three top commanders in Iran’s al-Quds force and four other officers, state TV has reported. No further details were provided about the meeting of the key decision-making body, but the president, Ebrahim Raisi, who chaired the meeting, said Iran would retaliate at the time of its own choosing – the standard formulation used by the Iranian regime when faced by such setbacks. “After repeated defeats and failures against the faith and will of the resistance front fighters, the Zionist regime has put blind assassinations on its agenda in the struggle to save itself,” Raisi said on his office’s website. The Iranian supreme leader, Ayatollah Ali Khamenei, who has the final say on all matters of state in Iran, also vowed revenge, saying: “We will make them regretful about the crime and similar acts.” Tehran now faces a strategic question of how harshly to respond, analysts said. Conflict has rippled across the Middle East since the onset of the Gaza war, but until now Iran has carefully avoided direct conflict with Israel while backing allies attacking Israeli and US targets. Israel has repeatedly targeted military officials from Iran, which supports militant groups fighting Israel in Gaza, and along its border with Lebanon. Monday’s strike in Damascus signalled an escalation because it struck an Iranian diplomatic mission. The building was reduced to rubble by the blasts, which blew out windows in nearby buildings and incinerated cars parked on the roadside in a leafy and upmarket suburb of the city. In keeping with its policy of not acknowledging its actions in the Middle East’s “shadow war”, Israel has not declared responsibility for the attack. However, a senior Israeli government official told Reuters that those hit had “been behind many attacks on Israeli and American assets and had plans for additional attacks”. The embassy itself “was not a target”, the official said. The UN security council will discuss the strike on Tuesday at a meeting requested by Russia. Iran’s mission to the UN warned that the strike could “potentially ignite more conflict involving other nations” and called on the security council “to condemn this unjustified criminal act”. The UN secretary general, António Guterres, condemned the attack on Iran’s diplomatic premises, calling on “all concerned to exercise utmost restraint and avoid further escalation”, his spokesperson said on Tuesday. “He cautions that any miscalculation could lead to broader conflict in an already volatile region, with devastating consequences for civilians, who are already seeing unprecedented suffering in Syria, Lebanon, the occupied Palestinian territory and the broader Middle East,” Stéphane Dujarric said in a statement. Among the dead were Brig Gen Mohammad Reza Zahedi, a senior commander in the al-Quds force of Iran’s Islamic Revolutionary Guard Corps (IRGC), a deputy commander, Gen Haji Rahimi, and Hossein Aminullah, the al-Quds chief of general staff for Lebanon and Syria. The US has distanced itself from the attack. White House security officials said they had been informed of the attack only as it was under way, and were not informed that a diplomatic building was being targeted. The Iranian minister of foreign affairs, Hossein Amir-Abdollahian, said the Swiss chargé d’affaires, who represents Washington’s interests in Iran, where the US does not have an embassy, ​​had been summoned. Amir-Abdollahian, quoted by the Iranian news agency Irna, said: “An important message was sent to the American government, since it supports the Zionist entity. America must take its responsibilities.” The US has itself assassinated IRGC leaders, but not inside diplomatic premises, and will be eager to ensure that any Iranian response is not directed at US assets. The three men killed represent the most senior figures in the IRGC in the region, and will be seen as a decisive blow. Iran will be concerned that Israel appeared to have had high-quality intelligence that such senior officers were all in the consulate, sending F16 jets to bomb the building in daylight. Syrian air defences mounted no apparent resistance. Diplomats worldwide will also be concerned that diplomatic premises are now regarded as legitimate targets. The Saudi Arabian foreign ministry said it “rejects the attack on diplomatic centres, which is a violation of international treaties and the principle of diplomatic immunity, under any pretext and under any justification”. John Sawers, the former chief of MI6, acknowledged the attacks would be regarded as an Israeli escalation since diplomatic premises are supposed to enjoy diplomatic immunity. Sawers said Iranian diplomatic premises were being abused by the Iranians for military planning and housing their senior military staff in Syria. He told the BBC that Israeli security sources believed the attacks on senior Iranian commanders, including the US assassination of the head of the al-Quds force, Qassem Suleimani, near Baghdad International airport four years ago, had “a wider impact on weakening Iran than was originally assessed”. “Israel believes that by taking out senior Iranian commanders they can undermine the line of control between Tehran and their so-called proxy militia in the axis of resistance in Hezbollah and Syria,” Sawers said. “The Iranians and Hezbollah have been very careful not to be pulled into a wider military conflict. Now the Israelis have seen that as a sign of weakness on the Iranian side – that they are not prepared to escalate – and that gives Israelis an opportunity to be more aggressive in their own operations without fear of pulling Iran into a state-to-state conflict with Israel.” Guardian Newsroom: The unfolding crisis in the Middle East On Tuesday 30 April, 7-8.15pm GMT, join Devika Bhat, Peter Beaumont, Emma Graham-Harrison and Ghaith Abdul-Ahad as they discuss the fast-developing crisis in the Middle East. Book tickets here or at theguardian.live