Ethnic Karen rebels last week captured the last army outpost in Myawaddy, which is linked to Thailand by two bridges over the Moei River, in the former Burma.

Renewed fighting erupted early on Sunday as the guerrillas attacked Burmese troops who had taken cover near the Thai-Myanmar Friendship Bridge, said Mae Sot district police chief Pittayakorn Phetcharat.

Phetcharat said about 1,300 people had fled into Thailand, according to the US-based Associated Press.

Myawaddy is a major trading point between the two Southeast Asian countries.

Thai authorities said Burmese had begun crossing the border since Friday after clashes erupted in several areas of Myawaddy.

The fall of Myawaddy is a major setback for the military, which seized power from the elected government of Aung San Suu Kyi in 2021.

Myanmar’s once-mighty armed forces have suffered a series of unprecedented defeats since October 2023.

They have lost swathes of territory, including border posts, to both ethnic armed groups, who have been fighting for greater autonomy for decades, and to pro-democracy guerrilla units that have taken up arms against the military.

The fighting, which included drone attacks by the Karen forces and airstrikes by the Myanmar military, had eased by midday on Saturday (local time) compared with earlier in the morning.

The Mae Sot police chief said Thai authorities were moving those who had fled to a safer area.

Footage from the Thai side of the border showed Thai soldiers standing guard near the bridge as the sound of explosions and gunfire echoed in the background.

People carrying children and their belongings waded across the river and were met on the bank by Thai officials.

Several people were seen sheltering in buildings along the riverbank on the Myanmar side.

Thai Prime Minister Prayuth Chan-ocha wrote on social media on Sunday that he was closely monitoring the situation on the border.

“I do not wish for these clashes to affect the territorial integrity of Thailand in any way, and we stand ready to protect our borders and the safety of our people,” he said.

“At the same time, we are also prepared to provide humanitarian assistance if needed,” Prayuth added, according to the AP.

Thailand in March delivered an initial batch of humanitarian aid to Myanmar for about 20,000 displaced people.

Thai authorities said a week ago that they were preparing to receive up to 100,000 people from Myanmar because of the fighting across the border.

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