ANKARA (Reuters) - A bomb blast killed one policeman and three civilians on Wednesday in Iran’s southeastern province of Sistan-Baluchistan near the Pakistan border, a local police official told the semi-official Tasnim news agency.

The predominantly Sunni Muslim province has been a hotbed of rebellion by Sunni Islamist militants against Iran’s Shi’ite authorities. Many of Iran’s Sunnis complain of discrimination, a charge denied by the state.

“A policeman was killed and several others were wounded after a booby trap bomb exploded in the town of Nikshahr,” Tasnim quoted provincial police chief Hossein Rahimi as saying.

Iranian media later reported that three civilians also died in the blast.

Rahimi said police were investigating the blast to determine who was responsible.