The Pentagon considered Monday that the likely leak of classified US documents, a large number of which are related to the war in Ukraine , poses a "very serious" threat to the national security of the United States.

The leak, which the Ministry of Justice opened an investigation about, appears to include assessments and classified intelligence reports not only on Ukraine but also on Russia, and highly sensitive analyzes of US allies.

Chris Meagher , Assistant Secretary of Defense for Public Affairs, told reporters that the documents circulating on the Internet pose "a very serious national security risk and have the potential to spread misinformation."

"We are still investigating how this happened, as well as the scope of this case. Steps have been taken to look closely at how and where this information was disseminated," he added.

Dozens of documents and images have been leaked on Twitter, Telegram, Discord and other sites in recent days, and some of them may have been circulating on the Internet for weeks, if not months, before these documents attracted media attention last week.

Meagher did not want to comment on whether these documents were authentic, saying only that a team from the Pentagon was conducting an evaluation.

The US official pointed out that some of the images circulating on the Internet appear to show sensitive information.

He said that there are "images that appear to show documents similar in format to those used to provide daily updates to our senior leaders about operations related to Ukraine and Russia, as well as other intelligence updates," noting that some of them "appear modified."

He explained that among these documents one was circulated on the Internet and it appears that it was modified to show that Ukraine suffered more human losses than Russia did, while the original document indicates that the opposite is true.