Four people, including the attacker, were killed and seven others wounded in a hostage-taking operation at the headquarters of a state institution in western Iran, state media said.
"A 37-year-old man from the Mostazafan Foundation in the city of Ilam entered a hall armed with a Kalashnikov and two bombs," the local police chief in the city of Ilam said.
Al-Qasi Mehr explained that the attacker "took members of the organization as hostages and started shooting and detonating a bomb, killing three people, including two women, and wounding seven."
Mehr indicated that the death toll was likely to rise, because four of the wounded were "in critical condition."
The Islamic Republic News Agency, IRNA, indicated that the attacker, who committed suicide at the site, had "personal motives". The agency published a video recording showing a number of policemen, armed men in civilian clothes, and members of the Iranian Red Crescent in the vicinity of the building.
The incident took place around 9:00 am (04:30 GMT) inside the Mostazafan Foundation, one of the most prominent charities in Iran.
Over the years, the Mostazafan Foundation has turned into a huge conglomerate that contributes to a number of key sectors in the Iranian economy, including oil and mining.