Tehran - Ten Iranian border guards were killed by Sunni militants in a “cross-border” attack on the frontier with Pakistan on Wednesday,Iranian news agency Tasnim reported.

The militant group called Jaish al Adl, or the Army of Justice, has claimed responsibility, the report said.

“10 border guards of Mirjaveh county in Sistan and Baluchestan Province were martyred in an ambush by the terrorists in the Pakistani border’s zero-point,” Tasnim said.

The semi-official Fars news agency said the gunmen fired on an Iranian patrol near the border.

Sistan-Baluchestan province in southeastern Iran has long been plagued by unrest from both drug smuggling gangs and separatist militants. The population of the province is predominantly Sunni Muslim; the majority of Iranians are Shias.

Jaish al Adl is a Sunni militant group that has carried out several attacks before against Iranian security forces with the aim of highlighting what they say is discrimination against Sunni Muslims and the ethnic Baluch in the province.

Four border guards were killed in July 2016 in the border region with Pakistan. Eight Iranian border guards were killed in clashes with Sunni rebels in 2015. Two years earlier, the Sunni militant group Jaish-ul-Adl killed 14 border guards in an attack.