Two motorbike riders lobbed grenade at a shop in Boulton Market on MA Jinnah Road.
The three injured of the attack were moved to Civil Hospital for medical attendance.
The shopkeepers of the market protested against the attack in the busy market area.
Man killed in firing
Two man were killed in separate firing incidents in the city, police said.
A man Javed killed in firing incident near Katti Pahari in Orangi Town. Another man died in shooting at Murtaza Chowrangi in Korangi.