Thousands of people have been moved from low-lying camps to safer shelter ahead of Cyclone Mahasen
The vessels hit trouble on Monday night after leaving Pauktaw township in Rakhine state, said a spokeswoman for the UN Office for the Coordination of Humanitarian Affairs (OCHA).
"They were travelling to another camp ahead of the cyclone," the spokeswoman added.
Kirsten Mildren, who works for the same UN agency, told Al Jazeera there was only one confirmed survivor from Monday's accident.
The victims were trying to escape Cyclone Mahasen which is expected on Thursday and Friday. The UN has warned the storm could lead to "life-threatening conditions".
|Al Jazeera's Everton Fox explains the weather impact of Tropical Cyclone Mahasen|
Myanmar state television said on Monday that thousands of people displaced by communal violence last year had been evacuated from makeshift camps to safer ground in the event of the storm.
The report said authorities had moved 5,158 people from low-lying camps in the Rakhine state capital, Sittwe, to safer shelter.
But human rights groups said that the government has been too slow to act, and ignored earlier warnings to provide shelter to displaced people.
"The Burmese government didn't heed the repeated warnings by governments and humanitarian aid groups to relocate displaced Muslims ahead of Burma’s rainy season," said Brad Adams, Human Rights Watch Asia director.
"If the government fails to evacuate those at risk, any disaster that results will not be natural, but man-made," he said.
Al Jazeera's Wayne Hay, reporting from Sittwe, said: "The eye of the storm is not expected to hit Myanmar, but the people in camps - home to more than 100,000 - are extremely vulnerable to conditions we may see over the next few days."
"These include strong winds, heavy rains and a possible surge from the ocean of up to 1.5 metres. The local government has been moving people ... but people in camps aren't trusting what they are trying to get them to do. Some say they are being asked to move to more dangerous places," our correspondent said.
The state television report said displaced people were moved in 10 other townships in western Myanmar where communal violence flared last year between Muslims and Buddhists, taking hundreds of lives and leaving more than 100,000 people homeless. It did not give the number of people evacuated in those locations.
Myanmar is a predominantly Buddhist country but about 5 percent of its 60 million people are Muslims. They face a growing anti-Muslim campaign led by radical Buddhist monks.
Cyclone Mahasen is expected to hit neighbouring Bangladesh on Thursday or Friday.
Images taken by NASA's Aqua satellite on Monday showed the storm's centre northeast of Sri Lanka with it packing winds of up to 50 knots (92km per hour). Those winds are expected to increase to 130km per hour as the storm moves north.
The space agency said it "sees a strengthening" of the storm and forecasts an upgrade to a Cyclone 1 level by Wednesday.
"The current forecast track ... takes the centre of Mahasen just north of Chittagong early on May 17 and into northern Burma," it said.
Officials in the Bangladeshi town of Cox's Bazar near the border with Myanmar said medical teams with as many as 30,000 Red Crescent volunteers were being formed.
In eastern India, authorities put 10 coastal districts on alert.
In 2008, Cyclone Nargis killed more than 130,000 people in Myanmar.
In 2007, Cyclone Sidr, packing winds of up to 240km per hour, left at least 3,500 people dead, levelled thousands of homes and forced the evacuation of 650,000 villagers in Bangladesh's southwest coast.