Rizwan Ahmend, a police official at the scene of the attack, said gunmen opened fire at the entrance.
It wasn’t immediately known how many gunmen were involved or whether they have been able to enter the stock exchange building itself.
Inside the stock exchange, broker Yaqub Memon told the Associated Press he and others were huddled inside their offices.
Heavily armed special forces have surrounded the building located in the heart of the city’s financial district, where the Pakistan State Bank is located as well as the headquarters of several national and international financial institutions.
Local television stations were showing police in full body armour surrounding the building, but still staying outside the high-walled compound.
Police said a bomb disposal squad has also been called to the stock exchange building and was trying to clear the building of explosive devises.
There were no other details and the fate of the attackers was not immediately known.
No militant group has claimed responsibility for the attack.
This is a developing story. Check back here for updates.