The deceased were identified as Md Ramjan Ali, 30, and Shorif Ali, 25, of Datidah village in the upazila.
Tariqul Islam, officer-in-charge of Mohammadpur Police Station, said Ramjan and Shorif along with three others went on a pleasure trip by boat in the river.
Suddenly, they a thunderbolt struck them around 6 pm leaving the duo dead on the spot and others injured.
Later, the injured were rushed to Mohammadpur Hospital immediately.
A case of unnatural death was filed with the police station, the OC added.
Comment: Elsewhere across the world in the last 2 days lightning has killed single individuals in the countries of India, Belize and Georgia.