Iran's Revolutionary Guards said on Saturday that Palestinian terrorist group Hamas' leader Ismail Haniyeh was slain in Tehran by a short-range projectile with a warhead of about 7 kg and vowed severe revenge.
This statement contradicts previous reports, which have been verified by the Jerusalem Post, that state that Haniyeh was killed by an explosive device that was planted in the room he was staying in while visiting Iran.
Wednesday's assassination has drawn fears of direct conflict between Tehran and its arch-enemy Israel in a region shaken by Israel's war in Gaza and a worsening conflict in Lebanon.
Revenge for the killing of the Hamas leader will be "severe and at an appropriate time, place, and manner," the Guards' statement added, blaming the "terrorist Zionist regime" of Israel for his death.
Iran and Hamas have accused Israel of carrying out the strike that killed Haniyeh hours after he attended the inauguration of Iran's new president.
Israeli officials have not claimed responsibility for the assassination.
The statement by the IRGC also accused the "criminal US government" of supporting the attack, which Iranian media said was in a northern suburb of Tehran.
Haniyeh was buried on Friday in Qatar, where he was based.
Yonah Jeremy Bob contributed to this report.