The explosion occurred near the Maula Dad Road area of Jacobabad district of the province, Senior Superintendent of Police in Jacobabad Sameer Noor Channa told Xinhua, adding that the target of the blast was apparently a police vehicle.
At least three police personnel were injured in the blast, the official said.
According to an initial investigation, the explosive material was planted in a motorcycle, said the police.
Following the incident, security forces and rescue teams rushed to the site and shifted the injured to a nearby hospital, where several among the injured are said to be in a critical condition.
No group or individual has claimed responsibility for the blast yet.