Thailand's foreign minister warned that his country would not tolerate any violation of its sovereignty, during a visit on Friday to the border with Myanmar following days of clashes that have dislodged junta troops from their positions in the neighbouring country.

Fighting between Myanmar's military and ethnic armed groups has rocked the border town of Myawaddy this week, sending people fleeing into Thailand, from where the boom of artillery shells and gunfire could be heard.

The conflict in Myanmar, sparked by the military's 2021 coup, regularly sends people rushing across the two countries' shared 2,400-kilometre (1,490-mile) border.

The recent clashes have raised concerns in Bangkok, with Thai Foreign Minister Parnpree Bahiddha-Nukara visiting the border on Friday.

"Our soldiers are guarding along the border, showing we are ready to protect, and not let anyone violate our sovereignty," he told reporters.

"Thailand has clearly stated that we will not allow anyone to violate Thai soil, we will not accept it," he said.

The conflict in Myanmar has provoked a Thai response before, with the kingdom scrambling jet fighters in 2022 after junta planes breached the border during operations against anti-coup fighters.

"I have talked to the army chief, we can't accept if our airspace has been trespassed," Prime Minister Srettha Thavisin reiterated earlier on Friday.

- Gunshots and prayers -

On Thursday, the Karen National Union (KNU) told AFP that displaced junta troops were sheltering near the terminus of one of the bridges on the Myanmar side.

AFP reporters said it appeared calm on Friday morning at the Moei river that divides the countries.

A Thai soldier standing guard at the border told AFP on Friday that he had heard gunshots and blasts in Myanmar during his night watch.

Over the border, a loudspeaker blared out Buddhist prayers.

Seven Thai armoured cars carrying soldiers arrived Friday morning to relieve the night watch, kicking up dust on the road.

A handful of trucks arrived on the Thai side from Myanmar over the "2nd Friendship Bridge", AFP reporters said.

No trucks were seen driving into Myanmar.

One truck driver arriving at a checkpoint in Thailand told soldiers he was "happy", adding "I thought I wouldn't be able to get back."

The Myanmar junta was sending reinforcements towards Myawaddy, military sources told AFP on Thursday.

A KNU source said its fighters and allied "People's Defence Forces" had clashed with the military on Friday at Kawkareik, about 40 kilometres (25 miles) away from Myawaddy by road, without giving details.

A resident of nearby Kyonedoe town said two civilians had been injured in artillery shelling on Thursday night.

- Battlefield losses -

The complete capture of Myawaddy would be a humiliating defeat for the junta, which has suffered a string of battlefield losses in recent months that have prompted rare criticism of its top brass by its supporters.

Junta spokesman Zaw Min Tun confirmed to local media late Thursday that junta soldiers "had to withdraw" from their base in Myawaddy, saying it was for their families' safety.

He said that the junta and Thai authorities were in discussion over the soldiers, but did not give any details about how many were involved.

AFP has contacted the Thai government for comment.

During his one-day visit, Parnpree also viewed preparations for a further influx of people fleeing Myanmar.

Thailand said this week it was prepared to accept 100,000 people from Myanmar.