Baloch separatists opened fire and hurled a grenade at the Pakistan Stock Exchange in Karachi yesterday, authorities said, killing four people including a policeman.
Three security guards were killed in the melee, while local police chief Ghulam Nabi Memon said all four assailants were shot dead.
The city's police force had earlier said six people died in the firefight but later revised the figure.
The Balochistan Liberation Army (BLA) claimed responsibility in a message sent to AFP.
Following yesterday's attack Pakistani authorities vowed to strike back against any group found responsible for the onslaught, promising to dismantle their networks and destroy their bases.