The Karen National Union (KNU) will investigate an alleged massacre of civilians on its territory, it said Wednesday, after state media accused its fighters of killing 25 construction workers.

State media published pictures Monday showing what it said were the bodies of 25 construction workers massacred by fighters from the Karen National Defence Organisation (KNDO) in the east of the country.

The KNDO is part of the Karen National Union -- a prominent ethnic armed group that has fought the military for decades and which had condemned the generals' coup.

"There have been media reports spreading since June 13th that 25 civilians... were killed by KNDO on May 31st, 2021," the KNU said in a statement.

"KNU (central) will form an investigating team to investigate to reveal the truth."

The group added it "cannot accept killing of civilians during fighting... We also have our restrictions to take action according to our related law regarding this kind of cases."

Since the coup the KNU has clashed sporadically with the Myanmar military along the Thai border.

In March its fighters seized a military post and the army retaliated with air raids, the first in more than 20 years in Karen state.

© AFP