At least four people were killed on Tuesday in a firing incident at a bus stand in Mastung district of Balochistan, said police officials.

"The incident happened when unknown gunmen opened fire on a vehicle. Four people were killed and one was injured in the firing incident in Mastung," said a police official.

"All deceased people belonged to Bangalzai tribe and initial investigations suggest that they were killed over some tribal rivalry," the official added.

Deceased and injured were moved to Civil Hospital Mastung and First Investigation Report has been filed in Mastung City Police Station.

The killings came hours after three suicide bombers stormed a police training college in Quetta, killing at least 60 and injuring over 100.

The attack was claimed by the militant Islamic State group (Daesh). The prime minister, the military high command and the opposition politicians are visiting the provincial capital following the deadly attack on police college.