Iranian authorities have not identifed the perpetrator yet.
A suicide vehicle bombing followed by an armed assault killed at least two people and wounded many more outside police headquarters in the port city of Chabahar in restive southeastern Iran on Thursday.
Rahmdel Bameri, Chabahar's acting governor, was among the Iranian officials who said two victims were killed by the December 6 car-bomb attack.
Mohammad Hadi Marashi, the deputy governor in charge of security, said the assailants tried to enter the city's police headquarters but "they were prevented by the guards and they detonated the vehicle bomb".
The official IRNA news agency said it was a auto bombing. No militant group immediately took responsibility for the attack.
"Iran will bring terrorists and their masters to justice", he wrote on Twitter.
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Footage showed smoke rising over the city.
On June 7, 2017 another co-ordinated Islamic State group attack on parliament and the shrine of Ayatollah Ruhollah Khomeini, the leader of Iran's 1979 Islamic Revolution, killed at least 18 people and wounded more than 50.
The attack was claimed by a Sunni separatist group called Jundullah (Soldiers of God).
Tehran often blames the United States, Saudi Arabia and Israel for backing groups to destabilize Iran, something its rivals deny.
Chabahar lies some 100 kilometres (60 miles) west of the Pakistan border and is home to a large, mainly Sunni Muslim ethnic Baluchi community which straddles the two countries.
Terror attacks in Shiite Iran are rare, but militants have stepped up action in recent months.