Heavy firing and explosions were reported on Saturday near the entrance of the Pakistan Army's General Headquarters in the garrison city of Rawalpindi, though it could not be immediately ascertained if there were any casualties.
Unidentified gunmen in a vehicle opened fire when soldiers at a check post near the General Headquarters tried to stop it.
This sparked an intense shootout that was ongoing as the soldiers returned fire with some top officers trapped inside, TV news channels reported.
The gunmen also lobbed five grenades at the Army Headquarters, Geo News channel reported.
An eyewitness told the channel there were five or six persons in the car and that he had seen one of them fall after being hit by the firing by the soldiers.
Security forces immediately cordoned off the area, bringing traffic to a standstill as the firing began.
A helicopter hovered over the area.
Another witness told a news channel that the firing was taking place in front of the office of the Inter-Services Public Relations, located within the General Headquarters. All staff of the ISPR were asked to stay inside their office.