A senior police officer confirming the incident said the cops were on routine patrolling when attacked by four unidentified assailants on two motorcycles at Bhangoria Goth area off Azizabad.
Killers who had attacked the cops from quite a close range managed to escape from the scene.
The constable wounded in the incident is being treated at a nearby hospital, said the official.
Those who succumbed to their injuries included sub-inspector Sikander and constables Ashraf and Asif.
In reply to a question he said authorities would also investigate as why, despite clear instructions, the police van was not covered by another of the police vehicle from safe distance to avoid such attacks, that were repeatedly registered a few months ago.
To avert casualties among police force in the metropolis a mechanism had been developed for their safety.