The accident occurred around 4:20 am on the Dinajpur-Gobindaganj Highway, said Ghoraghat Police Station officer-in-charge (OC) Nazmul Haque.
He said the identities of the deceased were not immediately known.
According to the OC, several trucks carrying mangoes were parked at the location.
The bus of Nabil Paribahan, travelling from Panchagarh to Dhaka, lost control and slammed into one of the trucks, he said.
Police and fire service teams rushed to the scene upon receiving information and rescued the injured, reports UNB.
The 15 injured were admitted to a local hospital, the OC added.