The mishap took place when the bus, which was coming from Chandigarh, in a bid to overtake another vehicle, swerved hit the tree, they said.
The injured, five of them stated to be in critical condition, have been admitted to a local hospital, police said.
Punjab Chief Minister Parkash Singh Badal announced an ex-gratia amount of Rs 1 lakh each to the next of kin of the deceased and Rs 25,000 to the seriously injured.