Myanmar anti-coup fighters briefly seized several border outposts after junta-aligned militia defected and joined the rebels, sparking days of heavy clashes, state media reported on Thursday.

Fighting has ravaged swathes of the country since the military's 2021 putsch, with some established ethnic rebel groups training and fighting alongside newer People's Defence Forces against the junta.

Rugged Kayah state on the border with Thailand has become a resistance hotspot, hosting thousands of democracy protesters turned PDF fighters.

Five border posts in the state manned by Border Guard Force (BGF) troops had come under "massive attacks" from anti-coup fighters between 13-19 June, state media said.

Border Guard Forces are made up of former ethnic rebels now working with the military in exchange for local autonomy and lucrative business rights.

They are often deployed side by side with regular troops.

Communications with a BGF post in Pantain, southeast Kayah, were cut for several days, according to the state-backed Global New Light of Myanmar.

Fighters at the BGF post "had betrayed the State and the Tatmadaw [military] by launching a rebellion" and joining anti-coup fighters, the report said, without specifying how many had defected.

The defectors had taken weapons and ammunition with them, the report said.

Backed by air and artillery strikes, the military had since retaken the post at Pantain on June 17, it added.

Another BGF post in Sukpaing was recaptured on June 27.

The military had suffered casualties in officers and other ranks, it said, without giving details.

Dozens of junta troops had defected, according to the opposition National Unity Government that is made up mostly of ousted lawmakers and which is working to overturn the coup.

PDF groups have surprised the military with their effectiveness, analysts say, and have dragged the military into a bloody quagmire.

In February, the junta admitted it did not "fully control" more than a third of the country's townships.
On Thursday 66 feet (20 meters) of a bridge on a highway linking commercial hub Yangon with the Thai border was mined and destroyed, the junta's information team said.

A drone attack on soldiers and officials inspecting the damage killed two and wounded ten civilians as well as some members of the security forces, it added.

An officer from the ethnic rebel Karen National Liberation Army told AFP that their troops and PDF fighters had mined the bridge.

The KNLA -- which has clashed with the military for decades -- has been a vocal opponent of the coup and provided shelter to dissidents working to oust the junta.

Battling fierce opposition on the ground, experts say the military is resorting to artillery strikes and air power.

On Tuesday a military airstrike on a village in northern Sagaing region -- another hotbed of resistance to junta rule -- killed ten civilians, locals and media reports said.

(AFP)

Members of the Karenni Nationalities Defence Force and Kareni Army at a checkpoint near Demoso, in eastern Kayah State, on October 19, 2021. (AFP)

Myanmar junta-aligned militia defect to rebels during heavy clashes