A police officer told Xinhua that the blast took place near a crossroad leading to the airport, adding that the nature of the blast is not known yet.
At least six people with serious burn injuries have been taken to a hospital, said the police officer.
Following the blast, fire engulfed several vehicles and nearby trees, local media reported.
An official from the Pakistan Civil Aviation Authority said that the blast site is not on the premises of Jinnah International Airport.
Police, security forces and rescue teams have reached the site and are taking part in the rescue operation.