US govt fears it has new mole after Snowden

US officials have confirmed that a new leaker is exposing national security documents, just over a year after ex-CIA contractor Edward Snowden blew the lid on NSA surveillance, according to a media report.

The existence of a second high-level leaker - separate from Snowden - has been mooted in intelligence and journalistic circles for some weeks, but was confirmed by US officials, according to a report by CNN.

Proof of the newest leak comes from national security documents that formed the basis of a news story published yesterday by the Intercept, the news site launched by Glenn Greenwald, who also published Snowden's leaks, the report said.

The Intercept article focuses on the growth in US government databases of known or suspected terrorist names during the Obama administration.

The article cites documents prepared by the National Counter-terrorism Center dated August 2013, which is after Snowden left the United States to avoid criminal charges.

Greenwald has suggested there was another leaker. In July, he said on Twitter "it seems clear at this point" that there was another.

Government officials have been investigating to find out that identity.

CNN, citing unnamed "US officials," reported that national security officers fear that they are now faced with a second source leaking classified intelligence from within their own ranks.

Speculation that there was a second source grew last month after the German magazine Der Spiegel published two articles containing apparent National Security Agency (NSA) leaks that were not, as in the past, explicitly sourced to Snowden, who remains in exile in Russia.

In a February interview, Greenwald said: "I definitely think it's fair to say that there are people who have been inspired by Edward Snowden's courage and by the great good and virtue that it has achieved."

"I have no doubt there will be other sources inside the government who see extreme wrongdoing who are inspired by Edward Snowden," he had said.

It is not yet clear how many documents the new leaker has shared and how much damage it may cause, the report said.

So far, the documents shared by the new leaker are labeled "Secret" and "NOFORN," which means it is not to be shared with foreign government.

That is a lower level of classification than most of the documents leaked by Snowden.

Government officials say he stole 1.7 million classified documents, many of which were labeled "Top Secret," a higher classification for the government's most important secrets.