Hamas chief Ismail Haniyeh and one of his bodyguards were killed after his residence was targeted in Tehran, Iran's Islamic Revolutionary Guard Corps (IRGC) confirmed in a statement.

A statement by the IRGC's Public Relations Department said the attack was carried out early Wednesday, adding that a probe is underway to find the cause of the incident.

The statement offered condolences to the people of Palestine, the Muslim world, and the Resistance Front's fighters over the Hamas leader's death.

A statement by Hamas says an "Israeli" raid killed the Palestinian group's leader Ismail Haniyeh in his residence in Tehran.

Mousa Abu Marzook, a member of Hamas political bureau, said the "cowardly" assassination of Ismail Haniyeh "won't go unanswered".

Earlier on Tuesday, Haniyeh had attended the inauguration of Iran's new president and met Iran's Supreme Leader.

The Palestinian leader was assassinated hours after praising Tehran's support for Hamas and Palestine during his meeting with Iran's President Masoud Pezeshkian.

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