LONDON - Three Iranian security personnel and three militants were killed in a cross-border attack on the frontier with Pakistan on Monday, Iran's Revolutionary Guards said in a statement posted on state media. The Guards said on Tuesday their ground forces killed a 'terrorist group' as they were trying to enter Iran near Mirjaveh border area in Sistan-Baluchestan province. Jaish al-Adl, a Sunni militant group that has carried out several attacks on Iranian security forces in Sistan-Baluchestan, said on its Twitter account on Tuesday that they killed 11 Iranian personnel on Monday, wounding several others. Jaish al-Adl said there were no casualties among their forces. 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 Shi'ites. Three Iranian security personnel were killed by militants in April.