The leak of highly sensitive US documents – many of them related to the Ukraine conflict – presents a “very serious” risk to US national security, the Pentagon said Monday, writes France24.

The breach is being investigated by the Justice Department and appears to include secret information on the war in Ukraine as well as sensitive analyses of US allies, whom American officials are now seeking to reassure.

A steady drip of dozens of photographs of documents have been found on Twitter, Telegram, Discord and other sites in recent days, though some may have circulated online for weeks, if not months, before they began to receive media attention last week.

The documents circulating online pose “a very serious risk to national security and have the potential to spread disinformation”, said Chris Meagher, assistant to the secretary of defense for public affairs, without confirming their authenticity.

“We’re still investigating how this happened, as well as the scope of the issue. There have been steps to take a closer look at how this type of information is distributed and to whom”, - Meagher told journalists.

Many of the documents are no longer available on the sites where they first appeared, and the United States is reportedly continuing to work to have them removed.

Meagher said US Defense Secretary Lloyd Austin was not initially briefed on the issue until the morning of April 6 – the day a New York Times story on the documents was published.