The pair have widely covered the military campaign in Rakhine although Reuters has declined to comment on whether they were specifically reporting on the mass grave in Inn Din.
"Action will be taken according to the law against villagers who were involved and security members who broke the Rules of Engagement", the post added.
The military claimed that they had rushed to Inn Din to protect frightened Buddhist villagers and had been attacked by "200 Bengalis" with sticks and swords, ten of whom were arrested and accused of having links to terrorists.
Although the soldiers should have handed over the 10 men to police, they made a decision to kill them at a local cemetery on September 2, because Rohingya terrorists had carried out other attacks by landmines and set fire to two police vehicles in Thinbawgwe village, the statement said.
Six soldiers were taken to a military hospital, border guard police official Sann Oo said by phone Saturday.
Robertson warned that the admission it did not represent a change of heart from the military.
"Then the military said it killed them because they had killed a man", he said.
More worryingly, it has emboldened nationalist voices who - like the military dictators that terrorised Myanmar - say journalists who challenge the official narrative should be punished for their treachery.
"But because the military has killed people in an unlawful manner, we are having many problems in the country, mostly in ethnic areas", he said.
The UN estimates only 60,000 Rohingya remain out of a population of 440,000 in the frontier township of Maungdaw.
"We view this as a wholly unwarranted, blatant attack on press freedom", said Stephen J Adler, president and editor-in-chief of Reuters.
Inn Din villager Hossain Ahammad said the slain men were "fishermen, farmers, lumberjacks and clerics".
US Ambassador Scot Marciel delivers an address on Myanmar-US relations in Yangon, May 10, 2016.
"We hope it is followed up by more transparency and by holding those responsible accountable", he said. "I would stress this should be done, not as a favour to the worldwide community, but because it's good for the health of Myanmar's democracy".
For a while, Rohingya Muslims in Myanmar have been subject to what a United Nations official called "textbook" ethnic cleansing.
Reporting on both sides of the Rohingya crisis has proven hard for members of the foreign press who are prohibited from entering the conflict-torn areas of Rakhine state and rarely granted interviews with top government officials.
The United States also declared the violence against Rohingya Muslims to be "ethnic cleansing" and President Donald Trump's administration announced on December 21 that it sanctioned the country's Maj.
The Myanmar government has also barred the media and some worldwide NGOs from entering the conflict zone.
"They have done absolutely nothing but carrying out their legitimate work as journalists", said James Gomez, Amnesty International's Director for Southeast Asia and the Pacific. The U.N. High Commissioner for Human Rights Zeid Ra'ad al-Hussein said the campaign amounts to ethnic cleansing that could include "elements of genocide". Translated by Khet Mar.