More than 655,000 Rohingyas have crossed into Bangladesh since August 25 a year ago, escaping a military crackdown in the Rakhine state, which many countries and human rights bodies have described as ethnic cleansing.
"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 in August", he added.
The captives should have been handed over to police, the army statement said, but with militants mounting continuous attacks and destroying two military vehicles, "there were no conditions to transfer the 10 Bengali terrorists to the police station and so it was chose to kill them".
Myanmar's civilian leader Aung San Suu Kyi said on Friday it was "positive" that the country's military was taking responsibility for the actions of troops, after the army said soldiers were involved in killing 10 captured Rohingya Muslims.
Since the August crackdown the army vigorously denied any abuses, instead locking down access to Rakhine state and accusing critics, including the United Nations, of pro-Rohingya bias and spreading "fake news".
"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 statement said.
The village of Inn Din previously featured in a chilling report by Amnesty International, which contains eyewitness accounts from seven villagers who described how vigilantes and the military looted and burned homes and shot people as they fled.
Inn Din, the site of the mass grave, was one of the hundreds of villages that was engulfed by violence during the August crackdown.
The government of Buddhist-majority Myanmar has refused to accept Rohingya Muslims as a minority group, even though they have lived in the country for generations. Such behaviour shows a contempt for human life which is simply beyond comprehension.
Aung San Suu Kyi said she knows the global community has great interest in the Rohingya issue.
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. "But this is false", he said.
Villagers had dug a pit and the men were ordered to enter it, where they were shot by the security forces.
Robertson warned that the admission it did not represent a change of heart from the military.
The pair - Wa Lone and Kyaw Soe Oo - were taken into custody after being invited to dine with police officers on the outskirts of Myanmar's largest city, Yangon.
The post on Facebook also gave the first confirmation of a mass Rohingya grave inside Rakhine state.