The bomber drove his vehicle, loaded with explosives, up to the police headquarters, provincial official Rahmdel Bameri told state TV. He said police officers blocked the vehicle and started firing at the driver, who then detonated the explosives.
State TV also aired footage of smoke rising over the city. The television report said two police officers were killed, lowering an earlier death toll of three without explanation.
Mohammad Mehran Aminifar, head of Medical Sciences University in Zahedan, the capital of southeastern Sistan and Baluchistan province, told state TV that 42 people were wounded, including four kids and a pregnant woman. Ten of the wounded were members of the police force, he said.
In a communique, the Sunni jihadist group Ansar al-Furqan claimed responsibility for the attack, according to the Washington-based SITE Intelligence Group, which monitors extremist activity online.
Iran Foreign Minister Mohammad Javad Zarif condemned the attack and warned "terrorists" that they will be punished. "Iran will bring terrorists and their masters to justice," he said on his Twitter account.
Ansar al-Furqan is known to operate in Sistan and Baluchistan province, which sees occasional attacks by Baluch separatists and drug traffickers. A year ago, the group claimed to have blown up an oil pipeline in Iran's southern Khuzestan province.
Chabahar, near Iran's border with Pakistan on the Sea of Oman, is home to a newly built port and is an economic free zone.
The attack comes as Iran's economy is reeling in the wake of the U.S. re-imposing sanctions lifted under Tehran's nuclear deal with world powers. While Iran still complies with the accord, President Donald Trump withdrew America over the deal in May, in part due to Tehran's ballistic missile program, its involvement in regional conflicts and its support of militant groups like the Lebanese Hezbollah.
While rare, Iran has been targeted in recent years by militant attacks.
In September, gunmen disguised as soldiers opened fire on a military parade in Ahvaz, killing at least 24 people and wounding over 60. Arab separatists and the Islamic State group both claimed the assault. Iran's supreme leader, Ayatollah Ali Khamenei, blamed Saudi Arabia and the United Arab Emirates for the attack, allegations denied by both countries.
A coordinated June 2017 Islamic State assault 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.
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