Pakistan has been hit by a wave of bombings in recent weeks in response to a military offensive against Taliban fighters in the northwest of the country.
But Thursday's was the closest to the capital since the launch of the offensive.
Rawalpindi, near Islamabad, is home to the headquarters of the Pakistani army and other state agencies.
In a separate incident, a roadside bomb exploded as a police patrol passed by on the outskirts of the northwestern city of Peshawar, killing two policemen and wounding four, including two civilians, Safwat Ghayur, a senior police officer, said.
Commenting on the day's violence, Imran Khan, Al Jazeera's correspondent, said: "We are hearing of a number of attacks today.
"This battle with the Pakistani Taliban is a shooting war.
"The Pakistani military is under immense pressure to rout the Pakistani Taliban.
"Afghanistan's Taliban can go into Pakistan as easily as Pakistan's Taliban can go into Afghanistan. Co-ordination is the absolute key to all of this."