BANGKOK — A tropical cyclone in the Andaman Sea is headed close to an area in Myanmar where tens of thousands of victims of ethnic and religious violence are living in makeshift camps, adding urgency to fears of what the United Nations has termed a looming “humanitarian catastrophe.”

Of the more than 130,000 people forced to flee their homes in rioting between Buddhists and Muslims over the last year in western Myanmar, around half are living in low-lying camps near the sea, the United Nations says.

Human rights organizations have issued repeated warnings that the displaced people are at risk of disease and hunger during the rainy season, which begins this month and continues until around September.

“We’re definitely very concerned,” said Vivian Tan, a spokeswoman for the United Nations refugee agency. “We are working around the clock, trying to get as many people out of low-lying areas and into decent shelters.”