The Islamic Republic's Supreme Leader Ayatollah Ali Khamenei will lead prayers for Haniyeh ahead of his funeral in Doha. Earlier, he threatened with "severe punishment" for his killing, AFP reported.
Haniyeh's death was announced by Iran's Revolutionary Guards, which said he and his bodyguard were killed in a strike on their home in the Iranian capital at 2:00 a.m. local time.
It came just hours after Israel targeted and killed senior Hezbollah commander Fuad Shukr in a retaliatory strike on the Lebanese capital Beirut, raising fears of a wider regional war.
Israel declined to comment on the Tehran strike.
Khamenei, who has the final say in Iran's political affairs, said after Haniyeh's death that it was "our duty to avenge his blood as he was martyred on the territory of the Islamic Republic of Iran."
The Hamas leader was in Tehran for the inauguration ceremony of the newly elected President Massoud Pezeshkian.
The Iranian president said that "the Zionists (Israel) will soon see the consequences of their cowardly and terrorist act."
Hamas political bureau member Musa Abu Marzouk also vowed to fight back, saying, "The assassination of leader Ismail Haniyeh is a cowardly act and will not go unanswered."
However, the international community has called for de-escalation and a focus on securing a ceasefire in Gaza.
UN Secretary-General Antonio Guterres said the strikes in Tehran and Beirut represented a "dangerous escalation".
He said all efforts must "lead to a ceasefire" in Gaza and the release of hostages taken during the Hamas attack on southern Israel on 7 October.
U.S. Secretary of State Anthony Blinken also pointed out that a ceasefire in Gaza was still an "imperative," and White House National Security Council spokesman John Kirby later added that the double killings were "not helping" regional tensions. | BGNES
