Initially police said a hand grenade was thrown near a water filtration plant across the road from the police station, but a senior Rawalpindi police officer Ahsan Younas later confirmed the blast was from a device planted on the side of the road.
Police said three of the casualties received deep wounds, while others were given medical care and discharged from the hospital.
No one immediately claimed responsibility for the explosion.
The Pakistani military’s headquarters and the offices of the country’s spy agencies are located in Rawalpindi, about 15 kilometers (9 miles) south of the capital, Islamabad
A similar roadside bombing struck Rawalpindi earlier this month, killing one person and wounding seven others near a busy bus terminal. In June, a roadside bomb went off in a crowded bazaar in the city, killing one and wounding 15.
Pakistan has witnessed scores of militant attacks on security forces and other targets in recent years.
In October, a powerful bomb blast kill at least eight students and wounded 136 others at an Islamic seminary on the outskirts of the northwestern city of Peshawar.