Classified documents that appeared online, with details ranging from Ukraine’s air defenses to Israel’s Mossad spy agency, have U.S. officials scrambling to identify the leak’s source, with some experts saying it could be an American.
Reporting by Idrees Ali; Additional reporting by Soo-hyang Choi and Hyonhee Shin in Seoul; Editing by Don Durfee, Daniel Wallis, Diane Craft and Gerry Doyle
U.S. officials said the investigation is in its early stages and those running it have not ruled out the possibility that pro-Russian elements were behind the leak, which is seen as one of the most serious security breaches since more than 700,000 documents, videos and diplomatic cables appeared on the WikiLeaks website in 2013.

Reuters