The U.S. 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 U.S. 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.

Reuters has not independently verified the documents' authenticity. U.S. 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 U.S. defense 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 U.S. secrets are shared.

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

The Pentagon on Sunday said in a statement that an interagency effort was assessing the impact the photographed documents could have on U.S. 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.

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