As the operation to eliminate them is underway, two militants have been killed and three people -- including one ranger and a police officer were injured, said  Pakistan media. 

Armed men opened fire at the head office of the port city's police, situated on the main artery of Sharea Faisal in Karachi. 

At least 8-10 terrorists are inside the police office with the exchange of fire still going on, said Pakistan's Geo News.

The inspector general of Sindh said that 2 terrorists were killed in the exchange of fire with the security officials while the operation is still underway to neutralise possibly up to five more terrorists in the Karachi police office, said Pakistan's ARY News. -- ANI