Iran's Revolutionary Guards said Saturday that Israel killed Hamas political chief Ismail Haniyeh using a "short-range projectile" launched from outside of his accommodation in Tehran.
"This terrorist operation was carried out by firing a short-range projectile with a warhead of about 7 kilograms - causing a strong explosion - from outside the accommodation area," the Guards said in a statement.
It added that Israel was "supported by the United States" in the attack.
Haniyeh was killed early Wednesday in the Iranian capital where he was attending the swearing-in of the new president, Masoud Pezeshkian.
Iran and Hamas have vowed to retaliate.
The Guards repeated their insistence that Haniyeh would be avenged and that Israel would receive "a severe punishment at the appropriate time, place and manner".
Israel, which has refused to comment on Haniyeh's killing, had earlier struck a Hezbollah stronghold in south Beirut.
That strike killed senior commander Fuad Shukr of the Lebanese militant group, as well as five others, including three women and two young children.
The killings are the latest of several major incidents that have inflamed regional tensions during the deadly Gaza war, which has killed at least 39,550 Palestinians in atrocities described as a genocide back UN groups, NGOs and a number of world leaders.
In Iran, the voices clamouring for revenge have intensified since Haniyeh's killing.
On Saturday, the ultraconservative Kayhan daily said retaliatory operations were expected to be "more diverse, more dispersed and impossible to intercept."
"This time, areas such as Tel Aviv and Haifa and the strategic centres and especially residences of some officials involved in the recent crimes are among the targets," the newspaper said in an opinion piece.