Initially police said the bomb was planted in an auto-rickshaw, but a Rawalpindi police statement later confirmed the blast was from a device planted on the side of the road.
No one immediately claimed responsibility for the explosion. Pakistani TV stations and videos on social media showed a burned-out rikshaw surrounded by police and emergency services.
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. In June, a similar roadside bomb attack struck a crowded bazaar in Rawalpindi, killing at least one and wounding 15.
Pakistan has witnessed scores of militant attacks on security forces in recent years.
In October, a powerful bomb blast ripped through an Islamic seminary on the outskirts of the northwestern city of Peshawar, killing at least eight students and wounding 136 others.