An attack on a courthouse on Saturday in Iran's southeastern province of Sistan and Baluchestan left five people dead and 13 injured, according to Iran's semi-official Tasnim news agency.

Gunmen from the Sunni Jaish al-Adl Baluch group carried out the attack, and  there may have been a suicide bomber involved in the assault in Zahedan, the capital of Sistan and Baluchestan, the semi-official Fars news agency said.

The report said explosions and gunfire were heard around the courthouse building, adding that Jaish al-Adl had in a statement taken responsibility for the attack.

Mehr news agency said a number of injured had been taken to hospital.

The Baluch human rights group HAALVSH, quoting eyewitnesses, said several judiciary staff and security personnel were killed or wounded when the assailants stormed the judges' chambers.

Sistan and Baluchestan Province, near the borders with Pakistan and Afghanistan, is home to Iran's Sunni Muslim Baluch minority, who have long complained of economic marginalization and political exclusion.

The province frequently sees clashes between security forces and armed groups, including Sunni militants and separatists who say they are fighting for greater rights and autonomy. The Iranian government accuses some of them of ties to foreign powers and involvement in cross-border smuggling and insurgency.

(With input from Reuters)