There were around 15 people in the boat, including Army and NDRF personnel when it capsized at around 4 PM in Barekuri area of Makum in the flood waters, the sources said.
Three children drowned, while five persons were missing, they said, adding, the rest were able to swim to safety.
An operation has been launched to search for the five missing persons.
The identities of the dead and the missing are yet to be ascertained, the sources added.