The Pentagon. Photo: David B. Gleason/Flickr.

The US national security community is grappling with fallout from the release of dozens of secret documents, including the impact on sensitive information-sharing within the government and ties with other countries, two US officials said.

Reuters has reviewed more than 50 of these documents, labeled “Secret” and “Top Secret,” that first appeared on social media websites in early March and purportedly reveal details of Ukrainian military vulnerabilities and information about allies including Israel, South Korea and Turkey.

The material did not draw much notice until a New York Times article on Friday (April 7).

Reuters has not independently verified the documents’ authenticity.

US officials have said some giving battlefield casualty estimates from Ukraine appeared to have been altered to understate Russian losses.

The leak was sufficiently alarming within the Pentagon that it referred the matter to the Department of Justice, which has opened a criminal investigation into the disclosure of the documents.

Two US defence officials, speaking on condition of anonymity because of the sensitivity of the matter, said the Pentagon was examining procedures governing how widely some of the most sensitive US secrets are shared.

Some of the documents, one of the officials said, would most likely have been available to thousands of people with US and allied government security clearances despite being highly sensitive, as the information directly affected those countries.

The Pentagon on Sunday (April 9) said in a statement that an interagency effort was assessing the impact the photographed documents could have on US national security as well as that of close American allies, a standard procedure known as “damage assessment” for leaks of classified information.

The first official said the number of people who had access to the documents underscores that sensitive information was perhaps being shared too widely with personnel who might not require the level of detail some of the documents contained.

“The Pentagon has needed to curtail the unbridled access to some of the most sensitive intel when they have no justifiable reason to have it,” the first official said.

The two officials said that although the leaks were highly concerning, many of them provided only snapshots of time in February and March – when they were dated – but did not appear to disclose anything about future operations.

Although the release of documents appears to be the most serious public leak of classified information in years, officials say it so far does not reach the scale and scope of the 700,000 documents, videos and diplomatic cables that appeared on the WikiLeaks website in 2013.

The first defense official said Pentagon investigators were trying to determine who would have an incentive to leak this kind of information.

Since the leak first came to light in March, the investigators have been pursuing theories ranging from someone simply sharing the documents to show off the work they were doing to a mole inside the US intelligence community or military, the first official added.

Daniel Hoffman, a former senior CIA undercover officer, said that given past activities of Moscow’s intelligence agencies, it was “highly likely” that Russian operatives posted documents related to Ukraine as part of a Russian disinformation operation.

He said such operations – meant to sow confusion, if not discord, among Russia’s adversaries – were a “classic” practice of Russian spy services to leak authentic documents in which they have inserted false information.

The aim, he said, appeared to be to drive a wedge between Ukraine and the United States, Kyiv’s largest provider of military support.