A special flight of Myanmar's state airline has used an airport in western Thailand on the countries' border. Thai media say the plane was sent to evacuate Myanmar government officials under attack from an ethnic minority force.

The flight arrived Sunday at an airport in Mae Sot and departed the same day. The Thai foreign ministry said Myanmar's military sought permission for the landing through diplomatic channels to bring back civilians, not soldiers.

The armed ethnic group Karen National Union has stepped up its offensive in Myanmar's southeastern state of Karen, bordering Thailand. It says it occupied a military facility on Friday, accepting the surrender of over 600 people, most of them soldiers.

The junta's arrangement of the airlift is seen as a sign it's losing ground near the border.

The apparent evacuation came after drone attacks by pro-democracy forces on a military headquarters and an air base in the capital of Naypyitaw on Thursday.

Ethnic minority forces have already taken control of areas near the border with Bangladesh in the western state of Rakhine and a border town near China in the northern state of Kachin.