At least two policemen were also injured during the fighting. They were rushed to a nearby hospital and their condition was described to be statble, a senior police official said on Monday.
The police launched a raid at militants hideouts in Karachi, eight militants were killed during the firing while four others died while being chased after they fled the scene, Xinhua quoted the official as saying.
The killed militants belonged to the outlawed Lashkar-e-Jhangvi and Tehrik-e-Taliban Pakistan militant group, the official said.
The police also recovered armed and ammunitions from the hideout of the militants.