U.S. national security agencies are reviewing how they share their most sensitive secrets inside the U.S. government, and dealing with the diplomatic fallout from the release of dozens of confidential documents, three U.S. officials said.

Investigators are also working to determine what person or group might have had the ability and motivation to release the intelligence reports, said one of the officials. The leaks could be the most damaging release of U.S. government information since the 2013 publication of thousands of documents on WikiLeaks.

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