By Mark Hosenball
LONDON (Reuters) - U.S. and European security authorities are investigating whether a previously unknown leaker provided sensitive intelligence documents to WikiLeaks about alleged U.S. spying on French politicians, according to sources familiar with the matter.
WikiLeaks, the transparency lobby group, on Tuesday released purportedly classified National Security Agency (NSA) documents alleging that the U.S. eavesdropping agency conducted surveillance on three successive French presidents - Jacques Chirac, Nicolas Sarkozy and incumbent François Hollande.
According to French media outlets, the documents show that Sarkozy considered restarting Israeli-Palestinian peace talks without U.S. participation, and that Hollande worried about the possible exit of Greece from the eurozone back in 2012.
U.S. and European security sources said the United States and allied governments were actively considering the possibility that someone other than former NSA contractor Edward Snowden provided the latest documents to WikiLeaks and its founder, Julian Assange.
The documents, some of which were published by French investigative website Mediapart, appear to include specific intelligence reports summarizing information collected by U.S. spies.
Two people familiar with documentation which Snowden acquired when he worked as an NSA contractor and later supplied to media outlets said that they do not recall seeing these kind of reports among those materials.
But some sources familiar with the investigations said it was still possible that these documents originated with Snowden.
In Washington, a National Security Council spokesman said on Tuesday: "We are not targeting and will not target the communications of President Hollande."
However, the statement did not address the question of any past surveillance of French leaders.
Previous reports based on the Snowden material alleged that the NSA had targeted the personal mobile phone of German Chancellor Angela Merkel. But the document exposing that surveillance was an NSA target list, not a report of specific intelligence which Washington collected from Merkel's phone.
The U.S. and European sources cautioned that they did not know for sure that Assange had developed a source other than Snowden inside U.S. intelligence. Assange has been in contact with associates of Snowden and helped arrange for him to flee from Hong Kong to Russia, where he was later granted asylum.
But until now, Assange, who three years ago took refuge in Ecuador's Embassy in London, has published few if any documents directly attributed to either Snowden's leaks or to the NSA.
Associates of Snowden have said that they believe he deliberately avoided giving sensitive U.S. documents to Assange.
(Story corrects to attribute comment to National Security Council spokesman, not National Security Agency, in paragraph 8.)
(Editing by Warren Strobel and G Crosse)