"The attack appears to be the work of one of the criminal gangs operating in Lyari," a police official said.
Grenade attacks and target killings are carried out frequently in different parts of Lyari which has been in the grip of lawlessness due to rival gangs who have their own turfs in the heavily populated town.
Lyari is one of the poorest and most violent neighbourhoods of Karachi where clashes between rival gangs linked to political and ethnic groups happen frequently.