The US claims that Russia or pro-Russian elements are likely behind the leak of classified military documents on social media.
The secret Pentagon documents discovered on 4chan, Twitter, Telegram and other websites related to Ukraine, the Middle East and China. They also appeared to detail US and NATO aid to Ukraine, but may have been altered or used as part of a misinformation campaign.
Three US officials told Reuters they believe Russia was behind the leak.
The Justice Department said it was investigating the leak, which was first reported by the New York Times on Friday.
The NYT The report came after the Pentagon said it was looking into how the handful of documents were posted to multiple social media sites.
The files contained, among other things, secret information sheets about China, the military theater in the Indo-Pacific and details about the Middle East and terrorism.
One of the leaked documents consisted of a map allegedly showing the status of fighting currently taking place in the eastern Ukrainian city of Bakhmut.
Other documents include Ukrainian air defense positions, combat equipment numbers and maps of combat situations in Kharkiv and southern Ukraine, the sources said New York Post.
A senior intelligence official said NYT that the leak is “a nightmare for the Five Eyes intelligence group,” which consists of the US, UK, Australia, New Zealand and Canada.
“We are aware of the reports of social media posts, and the department is looking into the matter,” Pentagon Deputy Press Secretary Sabrina Singh said Friday, shortly before the new documents surfaced.
After the documents were leaked, Ms Singh said in a statement: “The Ministry of Defense is actively reviewing the matter and has made a formal referral to the Ministry of Justice for investigation.”
At least five photos of slides and maps were also posted, with three of the photos marked “Secret” and one “Top Secret.” New York Post.