The IRGC announced in a statement on Wednesday morning that Haniyeh and one of his bodyguards were killed when their residence in the Iranian capital was hit in an attack.
The statement said the attack is under investigation and the results will be announced later in the day.
It also offered condolences to the heroic Palestinian nation, the Muslim Ummah (community), fighters of the resistance front and the noble Iranian nation over the martyrdom of the senior Palestinian resistance leader.
The Palestinian resistance leader was in Tehran to attend the swearing-in ceremony of Iranian President Masoud Pezeshkian.