Hamas leader Ismail Haniyeh was assassinated in Tehran, Iran's paramilitary Revolutionary Guard announced Wednesday, but nobody immediately claimed responsibility for the attack.
Israel was immediately blamed for the assassination after pledging to kill Haniyeh and other Hamas leaders over the terrorist group's Oct. 7 attack on the Jewish State, which killed 1,200 people and roughly 250 others were abducted, according to the Associated Press.
Haniyeh was in Tehran for Iranian President Masoud Pezeshkian's swearing-in on Tuesday. Pezeshkian was sworn in with chants of "Death to America, Israel."
On Tuesday morning, Iranian Supreme Leader Ali Khamenei posted on the social media platform X that he met with Haniyah and Palestinian Islamic Jihad Movement Secretary General Ziyad al-Nakhalah.
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Iran did not provide any details on how Haniyeh was killed. The incident is under investigation.
Analysts on Iranian state television immediately cast blame on Israel for the assassination.
Israel did not immediately comment, but it usually does not make public comments on assassinations carried out by their Mossad intelligence agency.
"The fact that such a high-ranking Hamas leader was assassinated on Iranian soil was an added bonus for Israel particularly directly after he participated in the inauguration ceremony of the new Islamic Republic president," Lisa Daftari, Middle East analyst and editor-in-chief at The Foreign Desk, told Fox News.
"It sends a clear message that Israel does not differentiate between the Islamic Republic and its proxies, Hamas and Hezbollah."
"We have seen Israel conduct very targeted and strategic hits against key players in the Islamic Republic such as nuclear scientists," Daftari continued. "We've also seen Israel conduct targeted hits on weapons depots and other critical infrastructures in Iran, Syria, Yemen and Lebanon."
"Given the numerous threats that surround Israel, it has been forced to use its military and intelligence capabilities to pinpoint direct threats and to strategically eliminate them. We assume at this point that the assassination of Haniyeh was made by the same calculations."
U.S. Defense Secretary Lloyd Austin said the U.S. government would seek to ease tensions but that it would help defend Israel if it were attacked.
Hamas said Haniyeh was killed "in a Zionist airstrike on his residence in Tehran after he participated in the inauguration of Iran’s new president."
"Hamas declares to the great Palestinian people and the people of the Arab and Islamic nations and all the free people of the world, brother leader Ismail Haniyeh a martyr," the statement said.
The group, in another statement, cited Haniyeh as saying that the Palestinian cause has "costs" and "we are ready for these costs: martyrdom for the sake of Palestine, and for the sake of God Almighty, and for the sake of the dignity of this nation."
Haniyeh left the Gaza Strip five years ago and was living in exile in Qatar. The top Hamas leader in Gaza is Yehya Sinwar, the mastermind behind the Oct. 7 attack against Israel.
Jonathan Conricus, a former IDF spokesman and now a Senior Fellow at FDD told Fox News Digital that "The assassination of Hamas terrorist Haniyeh in the Iranian capital, after Haniyeh reportedly met with the Supreme Leader of Iran, is almost poetic in choice of location and timing. If indeed accomplished by Israel, this assassination of a key architect and enabler of the October 7 massacre against Israel will send chills down Iranian spines, since it indicates the extent of intelligence penetration that Israeli security agencies have achieved in Iran"
The former IDF spokesman noted that, "Israel has degraded Hamas’ military capabilities over the last ten months to such an extent that Hamas will likely beg their Iranian masters or Hezbollah to retaliate in their stead. A meeting of senior Iranian terror-coordinators is underway in Tehran, after which the Iranian response may become clearer."
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An Israeli airstrike in April killed three of Haniyeh's sons and four of his grandchildren in Gaza.
More than 39,000 Palestinians have been killed and more than 90,000 wounded in the war in Gaza, according to the Hamas-run Gaza Health Ministry, although the count does not differentiate between civilians and terrorists.
The Associated Press contributed to this report.