At least five people were killed when gunmen stormed into the Karachi Stock Exchange building and opened fire on Monday morning.
All four assailants were shot down, the Pakistan police said.
The gunmen attacked the building’s main gate with grenades and then stormed the building, firing indiscriminately.
The premises have been evacuated, and the area around the Stock Exchange has been sealed off.
A security guard and a police officer were among the injured and were taken to a nearby hospital.
The building is in a high security zone that also houses the headquarters of many private banks.
Police said the militants had sophisticated weapons and were carrying a bag that may hold explosives.