Hamas chief Ismail Haniyeh killed in Iran

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 Defense Secretary Lloyd Austin said Washington would work to try to ease tensions but said the United States would help defend Israel if it were attacked.

"I don't think war is inevitable. I maintain that. I think there's always room and opportunities for diplomacy," he told reporters during a visit to the Philippines.

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.