The remote-controlled bomb was placed in a motorcycle parked outside a mosque in Sohrab Goth area of the city, police said, adding that some miscreants also resorted to aerial firing after the explosion.
"It was a low intensity blast that took place outside the mosque in Haji Gul Jannat township," a police official said.
Karachi, Pakistan's financial hub, yesterday saw at least 16 people getting killed in different parts of the city.
The city has seen a surge in sectarian violence in recent weeks.