The epicentre was in the city of Khuzdar, in Baluchistan province, at a depth of 26 kilometres (16 miles), meteorological official Zabih Ullah told AFP. The quake, which struck late morning, was also felt in surrounding towns and districts.
Pakistan straddles part of the boundary where the Indian and Eurasian tectonic plates meet, making the country susceptible to earthquakes.
It was hit by a 7.6-magnitude quake on October 8, 2005 that killed more than 73,000 people and left about 3.5 million homeless, mainly in Pakistan-controlled Kashmir.
A 7.7-magnitude earthquake devastated several areas in southwestern Baluchistan province in September last year. It killed at least 370 people and left 100,000 homeless.