Fighting erupted at 5am on Tuesday when Karen National Union (KNU) and Karen National Liberation Army (KNLA) forces attacked a Myanmar army outpost near the Thai border village of Mae Sam Laep in Mae Hong Son's Sob Moei district, said a ministry spokesman.
Myanmar government forces responded by launching airstrikes against the Karen forces in Hpapun district and a military base near Salawin National Park, he added.
Fighting between Myanmar government troops and ethnic armies has intensified since the military junta staged a coup against Aung San Suu Kyi’s government on February 1.
About 250 Thais in Mae Sam Laep had been evacuated to a safe zone in Huay Kong Kad, the spokesman said.
The 36th Ranger Forces Regiment and authorities in Sob Moei are giving assistance to the evacuees.
Thai and foreign evacuees would be treated in line with humanitarian principles and screened for Covid-19, added the spokesman.
“If the situation is likely to worsen and continue, evacuees will be transferred to another safe zone approximately 1 kilometre away from the first one," he said.
He added that government agencies in Mae Hong Son will launch a donation campaign if they cannot provide treatment for evacuees.