Unidentified gunmen opened fire on an office of Pak Sarzameen Party here on Sunday evening, killing two persons and wounding two others, Aaj News reported. The gun attack took place in Gulbahar Usmania Society, Nazimabad. According to police sources, unknown assailants opened fire on the PSP's office and escaped from the scene. Four people were injured in the firing. They were rushed to a nearby hospital, where two of them succumbed to their wounds, sources told.