
The Bengali-Muslims on board the motor boat are from relief camps in Pauktaw, Rakhine state.
The tragedy came amid evacuation of local victims by the local authorities to a safer place as a precaution against possible onslaught of cyclonic storm Mahasen.
The boat, which set out from Pauktaw on their own arrangement along with six other boats, collided with a huge rock at a river mouth where Kaladan River and Kywegu River meet and capsized on Monday 10 p.m., it said.
All six other boats were said to have been safe.
Thousands of local people living along the coast of Myanmar's western Rakhine state, especially Sittway, the capital of the state, have been evacuated onto hills as of Monday evening after repeated cyclonic storm warning over the last few days.
According to observations on Tuesday, cyclonic storm Mahasen over West central Bay of Bengal is centered at about 1,024 km West of Coco-Island, 880 km southwest of Pathein, 896 km southwest of Kyaukphyu(all Myanmar territories) and 400 km southeast of India's Vishakhapatnam.
The cyclonic storm Mahasen is moving northwards with its maximum wind speed estimated at 96 km per hour near the cyclone center.
It is likely to cross between northern part of Myanmar's Rakhine state and Bangladesh coast on Thursday evening.