Clashes broke out between police and an armed group following a bomb explosion in southeast Iran yesterday, the Fars news agency reported.
The device in the city of Zahedan caused no casualties, an official was quoted by the official IRNA news agency as saying today.
The clashes broke out in Zahedan late last night.
Zahedan governor Hassanali Nouri said police were pursuing those behind the blast.
He linked the bomb to the "massive participation of people in the funeral of victims of Wednesday's terrorist act".
A booby-trapped car blew up a bus owned by Iran's elite Revolutionary Guards on Wednesday, killing at least 11 people and wounding 31 others. Responsibility for that attack was claimed by a shadowy Sunni group, Jundallah (God's soldiers), which Iran has said is linked to Osama bin Laden's al Qaeda network.
Tehran has blamed Jundallah for past killings in the area bordering Pakistan. It was not clear whether the same group was behind the blast in Zahedan.
Iran has accused Britain and the United States of supporting ethnic minority rebels operating in sensitive border areas in an attempt to destabilize the country.
Iranian officials said five of those behind Wednesday's bombing, including the key suspect, were arrested by security forces.
The upsurge in unrest in Sistan-Baluchestan follows violence in Iran's oil-rich southwestern province of Khuzestan, which has a minority Arab population.
The United States accuses Iran of wanting to build nuclear weapons. Tehran insists its atomic work is aimed only at producing nuclear energy.