A police official in Guwahati said that five persons died on the spot and two were critically injured when the car in which they were travelling hit a stationary truck near the roadside in Bajali district.
The victims were returning home to Nalbari after attending the ongoing 'Raas Mahotsav' festival when their speeding car dashed the truck at Bhabanipur.
The two injured persons - Amir Khan and Kazi Chakra Ahmed - were immediately taken to Fakhruddin Ali Ahmed Medical College and Hospital and their conditions were stated to be very serious.
The deceased have been identified as Ashish Habib Khan, Mizanur Rahman, Royal Khan, Mizanur Khan and Moinul Haque.
In the second mishap, three persons died on the spot in a head-on-collision and another was critically injured when the speeding vehicle in which they were travelling hit a truck, parked on National Highway 17 at Golakganj in Agomoni area of Dhubri district.
The local people promptly took all the victims to Dhubri Medical College and Hospital. However, the three of them were declared dead upon arrival.
The victims were on their way from Gauripur to attend the ongoing annual 'Raas festival' at Cooch Behar in West Bengal.
The deceased have been identified as Dhanjay Roy, Bikash Kalita and Ramchand Roy while Khanindranath Pradhani, who was seriously wounded in the mishap, is currently undergoing medical treatment at the Dhubri Medical College and Hospital.
Police have launched a probe into the cause of both road accidents.
Preliminary investigations suggest that poor visibility and speeding might have caused both collisions.
Both accidents also caused a temporary disruption to traffic on the highway as police worked to clear the site.