Geneva: About 2,000 people from Myanmar have fled to Thailand after an upsurge of fighting in their homeland, the United Nations refugee agency said on Tuesday.

Jennifer Pagonis, spokeswoman for the office of the UN High Commissioner for Refugees (UNHCR), told journalists that 400 people crossed the border last week.

The influx began three months ago, she said.

Fighting has escalated since February in Myanmar involving the Karen National Union, which is the oldest and largest rebel force, still battling the country’s military regime.

Human rights groups say the upsurge has forced up to 11,000 people to flee their homes.

“The predominantly ethnic Karen refugees say their houses and villages have been burned and civilians killed,” said Pagonis.

“Many are very weak and suffering from illnesses such as malaria after a long, dangerous journey to the camps through heavily land-mined areas. Some also report that they had difficulties crossing the Thai border due to strengthened border controls.”

The refugees have been arriving at Thai government-run camps, mainly in the Mae Hong Son area in northern Thailand, Pagonis said.

The UNHCR is expecting more refugees to seek safety in Thailand in the coming weeks, she said.

Many of the refugees who crossed the border had first passed through a camp in Myanmar, she added.

“There, they say, hundreds more displaced Karen villagers are living in desperate conditions.”

There are currently 140,000 refugees from Myanmar living in nine border camps in Thailand, many of whom have been there for up to 20 years.