A bomb went off on a bus in the southern Pakistani city of Karachi on Saturday, Dec 29, killing six people and wounding 48, police and a hospital official said, according to Reuters.

Pakistan's commercial capital and biggest city has seen numerous militant attacks over the past 10 years and is also plagued by violence between rival ethnic-based factions.

The bus sustained serious damage in the explosion and a subsequent fire. While police said the bomb had been planted on the bus, provincial official Sharfud Din Memon said it was left on a motor-bike and went off as the bus passed.

Eight of the wounded were in critical condition, said Seemi Jamali, a doctor at Jinnah Hospital.