The deceased were identified as Humayun, 23, his younger brother Mamun, 21, and their maternal uncle Abdur Rashid, 37.
Patiya Highway Police said when the victims were going to Satkania from Lohagara a motorcycle crashed into a truck, leaving two of them dead on the spot.
Another victim was rushed to Lohagara Upazila Health Complex where doctors declared him dead on arrival, reports UNB.
Mohammad Mahbub, Officer-in-Charge of Patiya Highway Police Station, said a police team was sent to the scene for further investigation.