HONG KONG — At least 123,000 Rohingya have fled from western Myanmar into neighboring Bangladesh since late last month, the United Nations said on Tuesday, as a military crackdown has destroyed villages and killed hundreds.

In recent days, a constant stream of desperate people has marched through muddy fields while attempting to escape the violence. At least 46 Rohingya died last week when boats capsized while crossing a river between the two countries, the Bangladeshi authorities said.

The Rohingya are a largely Muslim ethnic group who mainly live in Rakhine State in western Myanmar, where they face severe restrictions on basic rights. On Aug. 25, Rohingya militants attacked several police outposts and a military base, killing at least 12 members of security forces.

The Myanmar military says it killed 370 Rohingya fighters in response to that attack. Soldiers and Buddhist vigilantes have carried out a campaign against people in Rakhine State, and those who have fled described seeing civilians shot from helicopters and homes burned to the ground.