The accident occurred on the Mymensingh-Sherpur Highway in the Shambhuganj-Alalpur village around 11am on Saturday, said Kotwali Model Police OC Mahmudul Islam.
The casualties have been identified as Yunus Ali, 55, Abdul Quddus, 35, Mustafizur Rahman and his wife Rahima Khatun, 52.
Two autorickshaws were involved in a head-on collision in Alalpur village before a truck rammed into the vehicles shortly afterwards, said the OC.
The injured have been admitted to the Mymensingh Medical College Hospital.