File Photo: In closing the Pentagon, the military could stop rotating staff officers in and out of northern Virginia, a think tank analyst writes. AFP
The breach -- which is being investigated by the Justice Department -- appears to include assessments and secret intelligence reports that touch not only on Ukraine and Russia but also highly sensitive analyses of US allies.
While the Defense Department is still reviewing the validity of photographed documents circulating online, they "appear to contain sensitive and highly classified material," Deputy Pentagon Press Secretary Sabrina Singh said in a statement.
"An interagency effort has been stood up, focused on assessing the impact these photographed documents could have on US national security and on our allies and partners," Singh said.
The Justice Department said Saturday it has been in touch with the Defense Department about the issue and had opened an investigation.
A steady drip of dozens of leaked documents and slides have made their way onto Twitter, Telegram, Discord and other sites in recent days, and new documents continue to surface.
US officials told the Washington Post that some documents appeared to have been manipulated but many were consistent with CIA World Intelligence Review reports that are shared at high levels within the White House, Pentagon and State Department.
Defense analysts say any breach of internal classified US documents would be both damaging and potentially embarrassing.
In addition, the leak would prove valuable to Moscow by showing how deep US intelligence has penetrated parts of the Russian military apparatus, US media said.
Other documents include apparent information about internal debate within the governments of US allies.
Among the documents, for example, were discussions about South Korea's debate on whether to provide the United States with artillery shells for use in Ukraine, The New York Times said.