The incident occured in the border village of Chengtimari under the upazila's Dangdhora Union around 10am on Friday.
The casualties have been identified as Anwarul Islam, 25, and Al Amin Mia, 17.
"Anwar and Al Amin went fishing in a marsh next to their home when lightning struck, burning most of their bodies. They died instantly,” said Shah Masud, chairman of Dangdhora Union Council.
Relatives later recovered their bodies.