ismail Haniyeh, the Doha-based political bureau chief of the Palestinian Islamist movement Hamas, speaks to the press after a meeting with the Iranian foreign minister in Tehran. AFP
"Brother, leader, mujahid Ismail Haniyeh, the head of the movement, died in a Zionist strike on his headquarters in Tehran after he participated in the inauguration of the new (Iranian) president," the movement said in a statement.
Haniyeh, 62, was targetted at 2am Tehran local time in his special residence in the Iranian capital using an “airborne guided projectile,” state-run news agency IRNA said.
In April, Haniyeh lost three of his sons and four of his grandchildren in an Israeli airstrike on a family home in Gaza.
Iran's Revolutionary Guards also announced the death, saying Haniyeh's residence in Tehran was "hit" and he was killed along with a bodyguard.
"The residence of Ismail Haniyeh, head of the political office of Hamas Islamic Resistance, was hit in Tehran, and as a result of this incident, him and one of his bodyguards were martyred," said a statement by the Islamic Revolutionary Guard Corps's Sepah news website.
Haniyeh had travelled to Tehran to attend Tuesday's swearing-in ceremony of Iranian President Masoud Pezeshkian.
The assassination of Haniyeh came only hours after Israel carried out a rare strike in the Lebanese capital Beirut targetting a top Hezbollah commander Fouad Shukur.
The Israeli army, which rarely claims assassinations, did not immediately respond to a request for comment on reports of Haniyeh's death.
A senior Hamas official said Wednesday that the killing of Haniyeh "will not go unanswered."
"The assassination of leader Ismail Haniyeh is a cowardly act and will not go unanswered," Hamas Political Bureau member Musa Abu Marzuk said in a statement.
Senior official Sami Abu Zuhri told Reuters that Haniyeh’s killing is a “grave escalation” and said Hamas is “confident of victory.”
Palestinian Authority President Mahmoud Abbas condemned Haniyeh's killing as a "cowardly act" and urged Palestinians to remain united against Israel.
The Palestinian cabinet and the secretary general of the Executive Committee of the Palestine Liberation Organization (PLO) also denounced the killing.
Haniyeh was elected head of the Hamas political bureau in 2017 to succeed Khaled Meshaal, but was already a well-known figure having become Palestinian prime minister in 2006 following an upset victory by Hamas in that year's parliamentary election.
Haniyeh has lived in exile for years and split his time between Turkey and Qatar.
He had travelled on several recent diplomatic missions to Iran and Turkey to galvanize regional support for the Palestinian cause and ensure reaching a ceasefire in the Israeli war on Gaza.
Up to the end, Haniyeh, considered by some as a pragmatist leader, led indirect negotiations with Isreal spearheaded by Qatar, Egypt, and the US to reach a prisoner swap deal and end the war.
Haniyeh maintained a working relationship with various Palestinian factions despite fractures between Hamas and some of its rivals.
He joined Hamas in 1987 when the group was founded amid the outbreak of the first Palestinian intifada against Israeli occupation 1987-1993.
Israel's genocidal war on Gaza has killed at least 39,400 people and wounded more than 90,000, mostly women and children, since 7 October.
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