Earlier in the day, the media reported that four people were killed and 30 injured.
According to the Dunya News broadcaster, all those injured have been hospitalized.
The blast occurred near a police car at a police station close to Bacha Khan Chowk, a neighborhood of Quetta. The police have claimed that terrorists had detonated explosives planted on several motorcycles near the site.
According to medics of the city's Civil Hospital, six of the 30 injured people are in critical condition.
Meanwhile, Samaa TV broadcaster reported that there were two policemen among those four people killed in the blast.
The site of the incident was cordoned off by the police and further investigation will reportedly continue on Wednesday.