Myanmar on Sunday began moving people into emergency shelters as a cyclone threatened to batter a violence-wracked region home to tens of thousands of internal refugees.

About 140,000 internally displaced persons (IDPs) living in flimsy tents or makeshift housing are seen as particularly vulnerable to cyclone Mahasen, which was gathering strength in the Bay of Bengal.

The cyclone is expected to make landfall somewhere near the Myanmar-Bangladesh border on Thursday morning, according to Myanmar's Department of Meteorology and Hydrology.

It said Mahasen, which was packing winds of up to about 100 kilometres (60 miles) per hour, was likely to intensify into a "severe cyclonic storm" within the next 24 hours, warning ships to be on alert.

The IDPs at particular risk are mostly stateless Rohingya Muslims uprooted by two outbreaks of deadly religious violence since June last year.

"There are people still living in temporary tents. Now we are moving as many of those IDPs as we can to the stronger permanent shelters," Myo Thant, a spokesman for the Rakhine state government, told AFP by telephone.

He said he was unsure of the capacity of the shelters -- which are located in the state capital Sittwe -- but acknowledged that there were not enough to accommodate all of the displaced people.

"The rest will be sent to stay with relatives in villages, and to nearby school buildings," he added.

Local radio issued warnings of the approaching cyclone while loudspeakers relayed messages to people in villages in Rakhine, one of Myanmar's poorest and most remote states.

The alerts revived memories of cyclone Nargis, which devastated Myanmar's Irrawaddy Delta in May 2008, killing about 140,000 people.

The UN's disaster assessment agency said preparations were under way to provide shelter for up to 13,000 displaced people in Sittwe, voicing "particular concern" for IDPs living in "poorly constructed camps."

"Many of the camps are located in low-lying coastal areas susceptible to tidal surge," it warned.

Myanmar views its population of roughly 800,000 Rohingya as illegal Bangladeshi immigrants and denies them citizenship.

New York-based Human Rights Watch last month accused Myanmar of "a campaign of ethnic cleansing" against the Rohingya, citing evidence of mass graves and forced displacement affecting tens of thousands.

Thousands of Rohingya have fled the Buddhist-Muslim violence on rickety boats, mostly believed to be heading for Malaysia.