A suicide car bomber attacked a police headquarters in the southeastern Iranian port city of Chabahar on Thursday, killing at least three people and wounding several others, state TV reported.
State television broke into its regular broadcast to report the attack, as such assaults are rare in the Islamic Republic.
He said police officers blocked the vehicle and started firing at the driver, who then detonated his explosives.
State authorities did not identify who was behind the attack. No militant group immediately took responsibility for the attack.
State TV also aired footage of smoke rising over the city.
Chabahar, near Iran's border with Pakistan on the Sea of Oman, is home to a new port recently built and is an economic free zone for the country.
The attack comes as Iran's economy reels in the wake of the US re-imposing sanctions lifted by Tehran's nuclear deal with world powers.
While Iran still complies with the accord, President Donald Trump withdrew America over the deal in part due to Tehran's ballistic missile program, its "malign behaviour" in the Mideast and its support of militant groups like Hezbollah.