Ismail Haniyeh, the political bureau chief of the Palestinian resistance movement Hamas, and one of his bodyguards were killed in their residence in the Iranian capital early on Wednesday.
They were killed after their residence was hit, the public relations office of the Islamic Revolution Guards Corps (IRGC) said in a statement.
The reasons behind the attack are under investigation and the details will be released later, the statement read.
Haniyeh was in Tehran to attend the inauguration ceremony of the new Iranian President Masoud Pezeshkian on Tuesday (July 30).