A bomb attack Sunday killed one person and wounded three in southeastern Iran, a state news agency reported, blaming a "terrorist group" linked to Tehran's enemies.

The attack occurred at about 9:30 am local time (0600 GMT) in Saravan city, the site of recent violence, in the restive Sistan-Baluchistan province.

A group "linked to global arrogance", a phrase often used in Iran for the United States and its allies, had carried out "the explosion at one of Saravan's squares, leading to one being killed and the injury of three citizens crossing the street," IRNA said.

Sistan-Baluchistan straddles the border with Pakistan and has a large, mainly Sunni ethnic Baluch population.

The province has long been a flashpoint for cross-border attacks by separatists and Sunni extremists.

The Sunday attack came almost a month after deadly clashes with fuel smugglers in Sistan-Baluchistan left two people dead, including a policeman in Saravan, according to Iranian authorities.

The UN Human Rights Office said at least 12 people were reportedly killed, two of them minors, and accused Iranian security forces of using excessive force.