After months denying any wrongdoing, Myanmar has admitted its forces helped kill 10 Rohingya in custody in an apparent bid to blame a few rogue soldiers for what the global community alleges is part of an organized ethnic cleansing campaign.

Since the August crackdown the army vigorously denied any abuses, instead locking down access to Rakhine state and accusing critics, including the U.N., of pro-Rohingya bias and spreading "fake news."

Then late on Wednesday it suddenly changed tune: an internal probe found four members of the "security forces" helped kill 10 Rohingya militant suspects at Inn Din village on September 2, leaving their bodies in a hastily-dug pit. "It was found that the incident was not submitted to superior levels," it said.

The unprecedented acknowledgment, relayed on the Facebook page of the office of army chief Min Aung Hlaing, rippled out across the rights community that has spent months piecing together allegations of numerous atrocities.

"This grisly admission is a sharp departure from the army's policy of blanket denial of any wrongdoing," said James Gomez, Amnesty International's regional director for Southeast Asia and the Pacific.

"However, it is only the tip of the iceberg," he added, urging independent investigation into other allegations.

Some observers say the army move is an attempt to retake control of the story after rumours of extra-judical killings at Inn Din and the surrounding area began to seep out.

According to U.N. estimates, more than 655,000 Rohingya Muslims crossed into Bangladesh after the Myanmar army launched a crackdown on suspected Muslim insurgents blamed for carrying out attacks on security posts in restive Rakhine state on Aug. 25. The U.N. and U.S. have described the military operation as "ethnic cleansing" of the Muslim minority, but have not released specific death tolls. The U.N. rights chief called for a fresh international investigation into Myanmar's abuses against its Rohingya Muslim minority, warning of possible "elements of genocide." The United Nations defines genocide as acts intended to destroy a national, ethnic, racial or religious group in whole or in part. A U.N. convention requires all countries to act to halt genocide and to punish those responsible.

The stateless Rohingya have been the target of communal violence and vicious anti-Muslim sentiment in mainly Buddhist Myanmar for years. Myanmar has denied citizenship to the Rohingya since 1982, and excludes them from the 135 ethnic groups it officially recognizes, which effectively renders them stateless. They have long faced discrimination and persecution with many Buddhists in Myanmar calling them "Bengalis" and saying they migrated illegally from Bangladesh, even though they have lived in the country for generations.