"Action will be taken against the villagers who participated in the case and the members of security forces who broke the Rules of Engagement under the law," the Myanmar military said in a statement posted to Facebook.
Before this admission, Myanmar's military had denied any wrongdoing in the violence that began in late August 2017 and has led to the exodus of more than 650,000 Rohingya from Myanmar to Bangladesh.
In a statement
, the military said around 200 "Bengali terrorists" attacked security forces with sticks and near the village of Inn Din, north of the provincial capital Sittwe, on September 1, 2017. The military "shot into the sky to disperse them (and) during that incident they captured 10 Bengali terrorists."
The 10 men were taken back to the village, where the "decision was made to kill them at the (Peyon) cemetery."
The statement said the next day security forces escorted villagers as they marched the detained men to the Peyon cemetery in Inn Din village. There, the villagers dug a pit and told the men to enter it. Some villagers entered the pit and attempted to stab or slash the men with swords and knives, after which a scuffle broke out.
"As some attacks coursed among them, four members of security forces near the pit shot them," the statement said.
A few months earlier, the statement said a local man had been allegedly killed by "Bengali terrorists," and his sons were among the group who escorted the men to the mass grave.
Both the UN and the United States say the violence that broke out last year and resulted in a massive refugee crisis on the Bangladesh border amounts to ethnic cleansing of the Muslim Rohingya from predominantly Buddhist Myanmar.
The Myanmar government says the bloodshed resulted from a military crackdown on militants who carried out co-ordinated attacks on border posts.
A recent Médecins Sans Frontières report
said at least 6,700 Rohingya were killed in attacks during the first month of the crackdown in Rakhine. In November, Myanmar's military said that 376 "ARSA Bengali terrorists" were killed in fighting between August 25 and September 5, referring to the Rohingya insurgent group.
This week, prosecutors in Myanmar sought charges under the country's Official Secrets Act -- a colonial hangover -- against two Reuters reporters, who are now facing up to 14 years in prison
The reporters had been reporting in Inn Din
village, where the mass grave was found, before their arrest, according to Myint Kyaw, a member of the Myanmar Press Council.
'Tip of the iceberg'
The military's admission of its role in the mass grave "is a sharp departure from the army's policy of blanket denial of any wrongdoing," James Gomez, Amnesty International regional director for Southeast Asia and the Pacific, said in a statement
"However, it is only the tip of the iceberg and warrants serious independent investigation into what other atrocities were committed amid the ethnic cleansing campaign that has forced out more than 655,000 Rohingya from Rakhine State since last August," he added.
The Myanmar statement said that security forces were unable to take the arrested men to the police station because of ongoing attacks and damaged vehicles so a "decision was made to kill them at the cemetery."
Amnesty said the military "showed a contempt for human life which is simply beyond comprehension."
Amnesty called on the UN to allow a fact-finding mission to uncover the "full extent of the violations."
Last month, Yanghee Lee, UN Special Rapporteur on the situation of human rights in Myanmar, was officially banned from the country
, after the government complained she was "not impartial and objective."
Media access to northern Rakhine State has also been tightly controlled, with most organizations denied access except on heavily supervised military tours.