The oil tanker, on its way from Guwahati to Rangiya, skidded and overturned when its driver tried to overtake another vehicle after crossing the Saraighat bridge, official sources said.
The tanker burst into flames immediately afterwards and eight fire tenders were pressed into service to douse the flame.
The entire area has been cordoned off and vehicles are stranded on about 12 km stretch on the national highway on both sides of the accident site, the sources said.
The driver, suspected to be in an inebriated state, and his helper were injured and admitted to Amingaon Civil Hospital, the sources added.