Hamas and its Iranian ally, the Islamic Revolutionary Guard Corps, announced that Haniyeh and a bodyguard were killed around 2am local time (7am Hong Kong time) in a precision “Israeli strike” on accommodation provided to him during his visit to attend the inauguration of Iranian President Masoud Pezeshkian on Tuesday.

“The timing, the inauguration of a new president, dares Iran to retaliate which forces [a] decision and course of action that Tehran likely didn’t anticipate or want,” Nasr said.

Israel has not claimed responsibility for Haniyeh’s assassination, but several of its ministers and opposition politicians issued statements celebrating the killing of the Hamas political chief as a victory for the Israeli security forces.

Prime Minister Benjamin Netanyahu’s administration announced its intention to wipe out the leadership of Hamas after the group attacked southern Israel last October, killing about 1,200 people. The conflict in Gaza has killed at least 39,445 people so far, the health ministry of the Hamas-run Palestinian territory said on Wednesday.

“Israel was very clear – Haniyeh was a dead man walking,” said Charles Lister, director of the Syria programme at the Middle East Institute, a Washington think tank.

Coming hours after the killing in Beirut, Haniyeh’s assassination had left the Middle East on an “absolute knife-edge now”, he said.

Hassan I. Hassan, editor-in-chief of New Lines Magazine, said the suspected Israeli strike against Haniyeh in Tehran would force Iran to retaliate.

Before it, the debate about rapid escalation between Israel and Hezbollah “hinged on Iran wanting to stay out of it or at least to see calculated attacks and counter-attacks”, he said.

In its April reprisal, Iran launched hundreds of drones and missiles at Israel to show its ability to overwhelm the Jewish-majority state’s air defences, without provoking a wider escalation.

“Now, both Hezbollah and Iran [will] feel compelled to respond,” Hassan said.

Iranian Supreme Leader Ayatollah Ali Khamenei has warned of “severe punishment” for Israel over Haniyeh’s death.

“The criminal Zionist regime [Israel] has murdered our guest in our house. There will be a severe punishment,” Khamenei said on his website.

Seyed Mohammed Mirandi, an Iranian academic who has advised Tehran on nuclear talks with the West, said: “Netanyahu is seeking a major escalation, and he will get it.”

The “Zionist regime bears sole responsibility for the consequences,” he added.

Calling for an immediate investigation into the assassination and restraint from all parties, the Malaysian foreign affairs ministry said: “Malaysia unequivocally condemns all acts of violence, including targeted assassination, and urges all peace-loving nations to join in denouncing such acts.”

Malaysian Prime Minister Anwar Ibrahim has issued a separate statement to condemn the assassination of Haniyeh.

“This was a murder of the most heinous kind, plainly designed to derail ongoing talks aimed at ending the carnage in Gaza that has claimed over 40,000 lives … Only the heedless and unconscionable will not see the need to intensify pressure on Israel to stop their murderous rampage.”

Anwar also defended his past meeting with Haniyeh, pointing to the Hamas leader’s desire for a peaceful Middle East and a Palestinian nation. “I mourn the loss of a dear friend and a valiant advocate for his people.”

Michael Young, a senior editor of the Carnegie Middle East Centre in Beirut, said the killings of Haniyeh and Hezbollah’s Shukr “underline that any restraining influence the US might have had on Israel is gone”.

Instead, the US “may have been aware” of both planned assassinations, and “may be moving to align more openly” with Israel, he said.

As such, a US air strike which killed four fighters of the pro-Iran group Kataib Hezbollah in Iraq on Tuesday “will be seen … as a coordinated effort by Washington and Israel to weaken Iran’s regional cards”, Young said.

“This doesn’t bode well for what is coming,” he added.

On the other hand, a restrained response from Iran and its allies could provide the Netanyahu administration with an opportunity to claim victory and start de-escalating the Gaza conflict.

“Netanyahu now has as close as it gets to a victory narrative in Gaza, which could finally allow for sincere ceasefire talks from Israel’s side,” said Andreas Krieg, an associate professor of defence studies at King’s College London.

Israel could now “preemptively signal de-escalation on both fronts [Gaza and Lebanon] to get out of a cycle of escalation that could bring it to the brink of collapse”, he said.

Mairav Zonszein, a senior Israel analyst of the Crisis Group, said the assassinations “do not make anyone safer and are not a strategic breakthrough”.

But it’s “important to understand that some Israeli officials do see it as a strategic gain that hastens a hostage/ceasefire deal”, she added.

Additional reporting by Joseph Sipalan