BANGKOK, Thailand - More than 30,000 Myanmar refugees living in camps in Thailand have been sent to third countries in what the United Nations said Wednesday had become the world's largest refugee resettlement operation.

Most of the refugees are Karen ethnic minority people who had been sheltered in nine refugee camps along the Thai-Myanmar border.

The U.N. High Commissioner for Refugees said 30,144 refugees have left Thailand to start new lives abroad since the resettlement operation began in January 2005. A UNHCR statement described it as the world's largest refugee resettlement operation.

But the camps remain home to 123,500 refugees and asylum-seekers.

"Some of the refugees have been here for nearly two decades. Some were born in refugee camps, grew up there and are now raising their own families in refugee camps," UNHCR regional representative Raymond Hall said Wednesday. "For them resettlement offers a way out of the camps and the opportunity for a fresh start in life."

The United Nations and human rights groups say that over the years the Myanmar military has burned villages, killed civilians and committed other atrocities against the Karen, who have long fought for autonomy from the central government.

Some activists have charged that Myanmar's ruling junta is waging a genocidal campaign against the Karen and other rebellious ethnic groups.

Hall said prospects for the refugees to return to Myanmar or settle permanently in Thailand were dim.

Nearly 21,500 of the resettled refugees have gone to the United States, while Australia has received 3,400 and Canada 2,600.

Other resettlement countries are Britain, Finland, Ireland, the Netherlands, New Zealand, Norway and Sweden.

Myanmar refugees are now leaving Thailand for resettlement at an average rate of more than 300 a week, the UNHCR said.