New Delhi, Jul 31 (IANS): Masoud Pezeshkian's first full formal day as Iran's President couldn't have started on a worse note. Hours before the day dawned, Hamas political bureau chief Ismail Haniyeh, a guest at his inauguration, was assassinated in Tehran, exacerbating what is already a toxic situation in the Middle East.

The development is awkward for Iran, given that it came while scores of international dignitaries were in the country, and personally for Pezeshkian, who had, in his inaugural ceremony a few hours back, underscored the need for peace in the region and a "constructive and effective engagement" with the world.

Whether the incident would presage escalation to a much wider conflict in the volatile region beyond Gaza and the Israel-Lebanon border remains to be seen, but the initial effect will be on the off-and-on negotiations for a Gaza truce and release of the remaining hostages.

Details of the assassination are still sketchy but according to the Islamic Revolutionary Guard Corps, a residence for war veterans in north Tehran where the Hamas leader was living was hit by a projectile at around 2 a.m., killing him and one of his bodyguards. There have not been any claims of responsibility, but Iran and the Hamas have blamed Israel and warned it of consequences.

Supreme Leader Ayatollah Seyyed Ali Khamenei said that the Israeli regime has "prepared the ground for harsh punishment for itself", as per Iranian media reports.

Iran considers its duty to take revenge for the assassination of Haniyeh who was martyred in the territory of the Islamic Republic of Iran, he added.

Pezeshkian's reaction was no less strong, as he stressed that the country would defend its "territorial integrity and dignity".

"...Yesterday I raised his victorious hand and today I have to carry his coffin on my shoulders", he said in a post on X, vowing that the "bond between the two proud nations of Iran and Palestine will be stronger than before" while Iran "will defend its territorial integrity and honour and would make the terrorist occupiers regret their cowardly action".

The IRGC, in a statement, warned "the Zionist regime" of a "harsh and painful response" for the assassination.

Acting Foreign Minister Ali Bagheri Kani said Iran "emphasises its right to respond to this aggressive provocative act as it deems it appropriate".

The targeting of Haniyeh comes shortly after Israel attacked Beirut to eliminate a top Hezbollah leader and claimed success, though the fate of Fuad Shukr was still unclear.

The immediate effect was on the truce talks.

Qatar, which was leading the negotiation efforts along with Egypt, reacted strongly to the assassination of Haniyeh, who used to live in exile in the country, with the Foreign Ministry terming it "a heinous crime, a dangerous escalation, and a flagrant violation of international and humanitarian law".

Qatar's PM and Foreign Minister Mohammed bin Abdulrahman bin Jassim Al Thani was more blunt. "Political assassinations & continued targeting of civilians in Gaza while talks continue leads us to ask, how can mediation succeed when one party assassinates the negotiator on the other side? Peace needs serious partners & a global stance against the disregard for human life," he said in a post on X.

Egypt's Foreign Ministry said that a "dangerous Israeli escalation policy" over the past two days had undermined efforts to broker an end to the fighting in Gaza.

"The coincidence of this regional escalation with the lack of progress in the ceasefire negotiations in Gaza increases the complexity of the situation and indicates the absence of Israeli political will to calm it down," it said in a statement.

In the long run, the targeting of Haniyeh, one of the most prominent Hamas leaders along with Khaled Meshal - the target of a bungled Israeli assassination plot decades back - and Mahmoud Zahar, could make for good optics for the purported beneficiary but is scarcely a strategic advantage.

Deemed a pragmatist, if not moderate, and open to political solutions, Haniyeh's removal from the scene could mean the leadership mantle switch back to shadowy - and more unrestrained - figures like Yahya Sinwar, perceived as the mastermind of the October 7, 2023 attacks.

The implications could not be promising for Israel - and the West at large, like after the 1967 Arab-Israeli War, when secular nationalist rulers like Egypt's charismatic Gamal Abdel Nasser were humbled, and Islamist fundamentalists gained ground. Israel repeated the same mistake in the 1970s, when it backed the incipient Hamas to undermine Yasser Arafat and the left-leaning and secular PLO, and in the process, ended up creating a bigger problem for itself.

The actions of the principal actors in days to come will determine if the Tehran assassination remains a one-off incident or a trigger to more instability, violence, and suffering.