Three of the deceased are—Joga and his wife, whose name could not be known immediately, and Ranjan, a 10-year old girl.
The identity of other two could not be known immediately, said Ashraful Islam PPM, assistant police super of Tangail Model police station.
The Bogra-bound truck fell into a roadside ditch full of water after the collision with the Dhaka-bound bus around 12.30pm, leaving five, who were riding on the truck, dead instantly, Ashraful said.
Twelve injured people out of 20 were admitted to Tangail Medical College Hospital.
The truck was carrying around 30 people, while there were no passengers in the bus.
Traffic movement came to a halt for half an hour after the accident, creating 15 kilometres long tail back on both side of the road.
Later, police eased the traffic jam.