Ethnic Karen rebels in Myanmar attacked a key town near the Thai border on Friday, residents and local media said, with the military junta calling in air strikes.
The Karen National Union (KNU) has been a vocal opponent of the military coup last year, and has provided shelter to dissidents working to oust the junta.
Its fighters, along with anti-coup "People's Defence Forces" have clashed sporadically with the military along the Thai border, sending thousands fleeing across the frontier for safety.
Friday's fighting began at 0100 GMT in Kawkareik, which sits on the road to a major border crossing with Thailand, a resident who requested anonymity told AFP.
The fighting was ongoing, they said, adding it appeared "armed groups" were trying to attack government offices.
"We are hearing heavy weapon shelling," they said, adding that three civilians were killed, and at least 15 were sent to hospital.
A KNU spokesman said its fighters were battling junta troops at various locations around the town.
The military called in multiple air strikes to support its troops on the ground, he said.
Both sides suffered casualties, he added, without providing details.
"We are hiding in the basement," a resident of the town told AFP.
"Just in front of my eyes, I saw a vendor killed in an explosion."
Other injured people were taken to hospital, they said.
A resident of a nearby town told AFP they had heard repeated artillery fire.
"About four jet fighters have flown across the sky many times," they said, requesting anonymity.
"We are frightened. Some people are leaving the town for safety."
Local media reported KNU fighters that many buildings were damaged by air and artillery strikes.
The junta said ethnic rebels and PDF fighters had attacked the town with "heavy artillery fire on residential areas, civil servants quarters and government offices" from early morning.
It said civilians were wounded and that its troops would "perform counter-terrorism action," without giving details.
Myanmar has more than 20 ethnic rebel groups, many of which hold territory in the country's border regions.
Following the coup that ousted Aung San Suu Kyi's civilian government in February 2021, dozens of PDF groups have also sprung up to fight the junta.
PDF fighters have conducted operations alongside troops from the KNU.
In June, Thailand scrambled fighter jets after a Myanmar warplane briefly breached its airspace during an operation against anti-coup fighters.
Stop forced returns
On Thursday, the United Nations urged Myanmar's neighbours to stop the forced return of its nationals, saying "countless lives" were being placed at risk.
The UN's refugee agency UNHCR said it was gravely concerned about multiple reports of refoulement -- the forcible return of refugees and asylum seekers -- since February 2021 from countries neighbouring Myanmar.
The agency is "urgently appealing to countries in the region to immediately stop forced returns of Myanmar nationals seeking safety from serious harm."
"We repeat our call on states to continue offering protection to Myanmar nationals fleeing for safety. This also includes ending the practice of indefinite detention of asylum seekers and refugees from Myanmar," said Gillian Triggs, UNHCR's assistant high commissioner for protection.
More than 2,300 people have been killed in the military's crackdown on dissent since the coup, which rights groups say includes razing villages, mass extrajudicial killings and air strikes on civilians. The junta blames anti-coup fighters for the deaths of almost 3,900 civilians.
In Magway region, the decapitated body of a high school teacher was left on grotesque display at a school in central Myanmar after he was detained and killed by the military, witnesses said on Thursday, marking the latest of many abuses alleged as the army tries to crush opposition to military rule.
According to witnesses’ descriptions and photos taken in Taung Myint village, the headless body of 46-year-old Saw Tun Moe was left on the ground in front of the school’s spiked gate and his head was impaled on top of it.
Neither the military government nor the state-controlled media have released information about the teacher's death.