Ten Iranian border guards were killed and three others were wounded Wednesday in a "terrorist attack" launched from inside Pakistan, Iranian state media said.
The border guards were patrolling in Mirjaveh in Sistan-Baluchestan province, southeastern Iran.
The militant group called Jaish-ul-Adl, or the Army of Justice, claimed responsibility for the attack, the state media said.
Sistan-Baluchestan province 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 Shi'ite.
Eight Iranian border guards were killed in clashes with Sunni rebels in 2015. Two years earlier, Jaish-ul-Adl killed 14 border guards in an attack