The explosion took place in Majeed colony, Landhi area, at a popular tea stall called Nadeem hotel and about 18 people were injured, some of them critically, police said.
"The police and bomb disposal squads have rushed to the spot but as yet the intensity and nature of the blast is not known," SSP Imran Shaukat said.
Earlier, seven people were injured in a grenade attack in Quetta. The attack took place on Saryab road.
"The injured included one security official and six civilians," a senior official said.