The injured included passersby besides the two policemen on duty nearby, the sources said.
Three critically injured persons were admitted to the Tinsukia civil hospital.
Police and security forces cordoned off the area and launched a search.
The sources said that it was an attempt by the anti-talk faction to make its presence felt.
There were reports of a group of hardcore ULFA militants sheltering in Dibrugarh and Tinsukia districts, their strongholds.