The incident took place early Thursday morning near the provincail governor compound.
Provincial scurity chief confirming the report said the explosion took place after explosives packed in a motorcycle went off, injuring four civilians.
He said the incident took place near the sports stadium where the National Front — main political opposition coalition of the Afghan government had a gathering.
In the meatime local residents and eyewitnesses in the area said another explosion was also heard near Guzara district highway.
No group has so far claimed responsibility behind the incident.