Suspected tribal insurgents ambushed a security patrol in resource-rich southwestern Pakistan, sparking gunbattles that killed three troops and 15 gunmen, an official said Sunday. Maj. Gen. Salim Nawaz said that five other troops were wounded in fighting late Saturday near the gas-producing town of Sui, about 180 miles southeast of the regional capital, Quetta. Authorities regularly blame attacks targeting security forces and gas installations around Sui on rebel tribesmen who are waging a violent campaign to force the central government to increase royalties for local resources. Salim said that the three troops were killed in the attack in Toba Mandrani area near Sui. Security forces retaliated, killing 15 insurgents, some near the scene of the ambush and others during subsequent clashes and search operations. The insurgency in the southwestern Baluchistan province is rooted in long-standing grievances by ethnic-Baluch leaders who say their province has been deprived of its due share of development funds. The Baluchistan unrest is separate from the Islamic militancy that Pakistan is facing along its northwestern frontier with Afghanistan.