The blast occurred on the Ring Road near Mal Mandi, Superintendent of Police Shafi Ullah told reporters.
The explosion, which targeted a police check post, damaged the structure's outer wall and a vehicle, he said.
Officials described the condition of one of the injured policemen as serious.
The wounded were taken to a nearby hospital.
Shafi Ullah said about five kilograms of explosives were used in the attack.
Security personnel cordoned off the area and launched a search operation.
No group claimed responsibility for the attack.
This was the fourth bomb blast in Peshawar in as many days.
Khyber-Pakhtunkhwa police chief Akbar Khan Hoti said policemen were again being targeted by militants.
On May 10, a security forces convoy was targeted with a roadside bomb at Bazidkhel on the outskirts of Peshawar though there were no casualties.
The following day, a senior police official had a narrow escape when his vehicle was targeted with a roadside bomb in Chughulpura area.
Yesterday, a policeman was killed and 17 others were injured when a police van was targeted with a bomb in Gulbahar area of Peshawar.
Islamabad: At least nine people, including a child and three policemen, were injured on Sunday when a bomb exploded near a police post in Peshawar, the fourth such attack in the northwestern Pakistani city in as many days.
First Published: Sunday, May 13, 2012, 12:26