BANGKOK, Thailand - Several Southeast Asian air force commanders will shun an upcoming meeting chaired by Myanmar's military rulers, officials told AFP, deepening the junta's regional isolation as it struggles to crush resistance.

The annual ASEAN Air Chiefs Conference gathers top air force leaders from the 10-nation bloc to discuss cooperation in defence, combating extremism and disaster relief.

Current chair Myanmar is set to host the meeting next week but at least three Association of Southeast Asian Nations (ASEAN) countries told AFP they will not send their top officials.

The junta has been accused of war crimes over air strikes carried out by its jets -- mostly Chinese and Russian-built -- in support of ground troops battling opponents of its 2021 coup.

Its air force chief Htun Aung, who will chair the conference, has been sanctioned by the United States and Britain.

The air force chiefs of the Philippines, Malaysia and Indonesia will not attend the meeting, officials told AFP.

Malaysia's air force chief will not attend, a spokesperson said, while the Philippine commander will send a video message to his counterpart rather than go in person.

Indonesia's air force chief "will not be attending and won't be sending anyone to represent him either", air force spokesperson Agung Sasongkojati told AFP without giving a reason.

At a summit this week, ASEAN accused the junta of targeting civilians in the grinding conflict sparked by its coup, and of ignoring a peace plan agreed with the bloc to end violence.

Indonesian Foreign Minister Retno Marsudi said there had been "no significant progress" in the five-point plan agreed with the junta more than two years ago.

The junta slammed that assessment as "one-sided".

ASEAN has barred junta officials from high-level meetings over their refusal to engage with the plan and their opponents.

Cambodian air force commander Soeng Samnang declined to comment on whether he would attend, and the defence ministry could not be reached for comment.

The air forces of Singapore, Brunei and Vietnam did not respond to requests for comment.

But Thailand's air force chief will make the trip to neighbouring Myanmar, a defence ministry official told AFP.

While ASEAN has halted high-level meetings with Myanmar's generals, Thailand has held its own bilateral talks with the junta and deposed democracy leader Aung San Suu Kyi in recent months, further dividing the bloc.

Activist group Justice for Myanmar said in a statement that ASEAN holding the air force meeting would "undermine its own commitments to resolve the crisis in Myanmar".

- War crime claims -
Amnesty International said last year the junta was likely using air strikes as "collective punishment" against civilians supporting anti-coup fighters, and in March the United Nations said the military had carried out more than 300 air strikes in the past year.

Also in March, the junta held a parade to mark Armed Forces Day, with flyovers by Russian-made Yak and Sukoi Su-30 jets.

The military bombed a gathering in northern Sagaing region in April that media and locals said killed about 170 people, sparking renewed global condemnation of the isolated junta.

Human Rights Watch said it had evidence the military had used a thermobaric "vacuum bomb" in the attack, saying it likely amounted to a war crime.

Air strikes on a concert held by a major ethnic rebel group in northern Kachin state killed around 50 people last October.

The junta has said reports civilians were among the dead were "rumours".

AFP has contacted a Myanmar junta spokesman for comment.