Gunmen shot dead three policemen deployed at a railway bridge in Pakistan's Hassanabdal town, media reports said on Sunday.
Bodies of the three policemen were found Sunday morning inside their quarters next to the tracks in the Hassanabdal town, located around 50 km from the capital city, Islamabad.
It is believed the trio was slain in their sleep, the Geo News television channel quoted local police as saying.
Investigators could not discover a reason for the killings, and there was no immediate claim of responsibility from any group.
Hassanabdal is part of the Punjab province's Attock district, which shares boundaries with the militant north-western region.
Islamist insurgents frequently attack police, but such strikes are less common in Punjab.