Four gunmen attacked the Pakistani stock exchange in Karachi, killing at least two people and wounding others before police shot them dead.
The assailants launched a grenade attack at the main gate to the building and opened fire but police say they failed to make it to the trading floor.
Staff inside took refuge in locked rooms and many were evacuated. Security forces are searching the area.
Militants from the Baloch Liberation Army say they were behind the attack.
Ethnic Baloch groups have fought a long-running insurgency for a separate homeland and a greater share of resources in Pakistan’s Balochistan province.
Pakistan has suffered years of militant violence, mostly by Islamist groups, but attacks such as this one have become rare in recent years.
Monday’s attack began when the militants armed with automatic rifles threw a grenade and then began firing at a security post outside the stock exchange.
“The attackers came in a silver Corolla and were stopped by police at the gate outside where the exchange of fire took place,” Sindh police additional inspector general Ghulam Nabi Memon told BBC Urdu.