Islamabad, Pakistan (CNN) -- Three civilians and a police officer were killed Wednesday after militants fired two rockets at security checkpoints in Pakistan's western city of Quetta. Police spokesman Abdullah Afridi said militants fired the rockets along Saryab Road, injuring an additional 15 people. Earlier this month, four civilians were killed and 10 were injured when a bomb exploded near a security patrol in Pakistan's Balochistan province, police told CNN. Balochistan has long been plagued by sectarian violence between Sunnis and Shias, and separatist Baloch militant groups who demand political autonomy. Quetta, Balochistan's provincial capital, is widely believed to be a safe haven for senior leaders of the Afghan Taliban, but rarely are militant attacks in Balochistan linked to them.
3 civilians and a police officer were killed Wednesday in a rocket attack . Police say the attack injured an additional 15 people . Quetta is Balochistan's provincial capital .