ISLAMABAD, April 25 (Xinhua) -- At least four paramilitary troops were killed and three others injured in an attack in Pakistan's southwestern Balochistan province on Friday, official sources said.

The incident happened on the outskirts of Quetta, the provincial capital city, where a vehicle carrying the bomb disposal squad was targeted by an improvised explosive device, the sources from the city's police told Xinhua.

"The team, belonging to the Frontier Corps, was conducting routine operations in the area when their vehicle was struck by the explosion," the sources added.

The injured troops were shifted to a nearby hospital for treatment.

Security forces cordoned off the area and launched a search operation to trace the perpetrators.

No group has claimed responsibility for the attack yet.

Balochistan has witnessed sporadic violence in recent years, with security personnel often targeted in attacks claimed by various militant groups. ■