In the early hours of Tuesday, soldiers from the KNU's Fifth Brigade attacked and razed a military outpost in eastern Karen state near the Salween river -- which demarcates part of the border shared with Thailand.

The attack was confirmed by both the KNU and junta spokesman Zaw Min Tun, who vowed to "take action".

By around noon, the military retaliated by launching air strikes north of the base, according to Sithichai Jindaluang, the Thai governor of bordering Mae Hong Son province.

"Thailand does not support either side but concentrates on ensuring the safety of Thai nationals," he said. His province has also devised a "refugees management plan".

Sithichai added that a stateless woman who lives in Mae Sam Laep was shot in the leg, caught in the crossfire. She was treated at hospital and in a stable condition, he said.

Last month, after the KNU overran a military outpost in the same region, the junta responded with multiple air strikes at night.

Since then, fighting between the two sides has displaced some 24,000 civilians, including more than 2,000 who crossed the river to seek refuge in Thailand before they were pushed back by border authorities.

Villagers on the Thai side of the border had already fled their homes, said Hkara, an ethnic Karen resident, adding that she heard explosions and gunfire from inside Myanmar around 5 am.

"Nobody dares to stay," she said.

AFP