JAKARTA: The Association of Southeast Asian Nations (ASEAN) remains committed to a peace plan agreed with Myanmar's military rulers, its chair Cambodia said on Thursday, even as some countries raised concerns over the failure to implement a plan agreed with the junta 18 months ago.

A special meeting of the group's foreign ministers was held in Jakarta to discuss the stalled peace plan, though there were no representatives from Myanmar present.

Myanmar's generals have been barred from high-level ASEAN meetings since last year, when the army ousted Nobel laureate Aung San Suu Kyi's elected government, detaining her and thousands of activists and launching a deadly crackdown that has given rise to armed resistance movements.

The junta has done little to honour its commitments to the so-called five-point peace "consensus" agreed with the group last year, sparking growing frustration among some members.

The five-point consensus includes an immediate halt to violence and starting dialogue towards a peace agreement, as well as allowing an envoy of the ASEAN chair to facilitate mediation and for ASEAN to provide humanitarian assistance.

A spokesperson for Myanmar's military government did not answer a call seeking comment on Thursday.

The head of the junta has previously blamed a lack of progress implementing the plan on instability in the country and the challenges of the pandemic.

ASEAN foreign ministers and representatives had agreed the bloc should be "even more determined" to bring about a peaceful solution in Myanmar as soon as possible, the chair said in a statement, noting that Myanmar's situation remained "critical and fragile".

"The foreign ministers expressed concern and disappointment over no significant progress on the five-point consensus implementation," Indonesian Foreign Minister Retno Marsudi told a news conference after the meeting.

Recent weeks have seen some of the bloodiest incidents in Myanmar, including the bombing of Myanmar's largest prison and an air strike in Kachin State on Sunday, which local media said killed at least 50 people.

"The violent acts need to stop immediately. And Indonesia had mentioned that this request needs to be delivered to Tatmadaw (Myanmar's military) immediately," said Retno.

ASEAN has a longstanding policy of non-interference in members' sovereign affairs, but some nations have called for the bloc to be bolder in taking action against the junta.

The top U.S. diplomat for East Asia, Daniel Kritenbrink, on Wednesday described the situation in Myanmar as "tragic" and said the United States, which has imposed sanctions on the military leadership, would take "additional steps to put pressure on the regime," but did not elaborate.