Two of them have been hospitalised, while the SHO received minor injuries, Mr Gupta said.
According to eyewitnesses, they were waiting for their bus to leave for New Delhi when a sudden blast took place and they ran for cover.
The police vehicle was probably the target but the grenade missed it and exploded near the vehicle, the witnesses said.
Soon a number of people gathered at the bus stand area and raised anti-Pakistan slogans.
The area has been cordoned off and searches launched to track down the suspected terrorists, the SSP said.
Meanwhile in Srinagar, terrorists on Thursday night hurled a grenade towards the CRPF camp but there was no loss of life in the incident, police said.
Terrorists lobbed a grenade on the CRPF camp at the Brari Pora in Nawakadal area of the city, a police official said.
Further details were awaited, the official said.