The Southeast Asian nation has been in chaos since a February coup, with more than 1,100 killed in a crackdown on dissent, according to a local monitoring group.

On Friday, the UN said it feared an even greater human rights catastrophe amid reports of thousands of troops massing in the north of the country.

Special Rapporteur on Myanmar Tom Andrews warned the UN General Assembly that the tactics were "ominously reminiscent" of those deployed before a bloody crackdown on the Rohingya minority in 2016-2017.

The junta slammed the report on Sunday and accused the UN of using human rights "as a political tool to intervene in the internal affairs of Myanmar".

The report would "only lead to further division among (the) nation and incitement to internal violence", the junta-appointed Ministry of Foreign Affairs said in a statement.

Almost nine months after seizing power, and unable to stamp out opposition to their regime, the generals are under increasing international pressure to engage with their opponents.

Last week, the Association of Southeast Asian Nations (ASEAN) decided to exclude junta chief Min Aung Hlaing from an upcoming summit of the 10-country bloc over doubts about his commitment to defuse the bloody crisis.

It called instead for a "non-political representative" to attend the October 26-28 summit, which the junta said will be "difficult to comply" with.