Hamas leader Ismail Haniyeh was assassinated in the early hours of the morning in Iran, the Palestinian group said on Wednesday, drawing fears of wider escalation in a region shaken by Israel’s war in Gaza and a worsening conflict in Lebanon. Iran’s Revolutionary Guards confirmed the death of Haniyeh, hours after he attended a swearing in ceremony for the country’s new president, and said it was investigating. Iran’s President Masoud Pezeshkian said on Wednesday that it will “defend its territorial integrity, dignity, honour, and pride, and will make the terrorist occupiers regret their cowardly act” of assassinating Hamas leader Ismail Haniyeh in Tehran, according to Iranian media. There was no immediate comment from Israel. The Israeli military said it was conducting a situational assessment but had not issued any new security guidelines for civilians. Prime Minister Benjamin Netanyahu was expected to meet for consultations with security officials at midday (0900 GMT). US Secretary of State Antony Blinken said that the United States was “not aware of or involved” in Haniyeh’s killing. “I can’t tell you what this means. I can tell you that the imperative of getting a ceasefire, the importance that has for everyone, remains,” Blinken said, according to a transcript shared by his staff from an interview with Channel News Asia in Singapore. The news, which came less than 24 hours after Israel claimed to have killed the Hezbollah commander it said was behind a deadly strike in the Israeli-occupied Golan Heights, appears to set back chances of any imminent ceasefire agreement in Gaza. “This assassination by the Israeli occupation of Brother Haniyeh is a grave escalation that aims to break the will of Hamas,” senior Hamas official Sami Abu Zuhri told Reuters. He said Hamas, the Palestinian group that ruled Gaza, would continue the path it was following, adding: “We are confident of victory.” Haniyeh, normally based in Qatar, has been the face of the Palestinian group’s international diplomacy as the war set off by the Hamas-led attack on Israel on Oct. 7 has raged in Gaza, where three of his sons were killed in an Israeli airstrike. Appointed to the Hamas top job in 2017, Haniyeh has moved between Turkey and Qatar’s capital Doha, escaping the travel curbs of the blockaded Gaza Strip and enabling him to act as a negotiator in ceasefire talks or to talk to Hamas’ ally Iran. Qatar, which has been brokering talks aimed at halting the fighting in Gaza, condemned Haniyeh’s killing as a dangerous escalation of the conflict. China and Russia have also condemned the assassination. Iran’s Supreme Leader Ayatollah Ali Khamenei said Israel had provided the grounds for “harsh punishment for itself” and it was Tehran’s duty to avenge the Hamas leader’s death. Iranian forces have already made strikes directly on Israel earlier in the Gaza war. Pakistan has strongly condemned the assassination of Ismail Haniyeh, head of Hamas’ political bureau, in Tehran. The Foreign Office spokesperson expressed deep condolences to Haniyeh’s family and the Palestinian people, condemning all forms of terrorism, including extrajudicial killings. “We express our sympathies to his family and the Palestinian people,” the spokesperson stated. “Pakistan condemns terrorism in all its forms, including such extrajudicial killings.” The spokesperson also expressed Pakistan’s deep concern over the increasing Israeli aggression in the region. “Pakistan is deeply concerned about the growing Israeli adventurism. These actions are a dangerous escalation in an already unstable region and undermine peace efforts,” the statement read.