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.

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 Associated Press contributed to this report.