An unidentified police officer told Dawn News another civilian was critically injured in the incident in the vicinity of a bus stop.
"The suicide bomber was coming to Quetta to cause maximum damage, when his own suicide jacket went off", he said.
Nearby shops and buildings were damaged by the blast.
In another incident, unidentified gunmen attacked two cargo trucks traveling from Karachi to Quetta and set fire to them, Dawn said. Both drivers were injured.