WASHINGTON - The New York Times reported on Saturday that the National Security Agency, the main US government surveillance organization, had since 2010 used data it gathered to map some Americans' "social connections that can identify their associates, their locations at certain times, their traveling companions and other personal information."

In the latest revelation of the activities of the NSA, which have prompted concern about previously unknown intrusion into Americans' privacy in the name of protecting against terrorist and other foreign attacks, the newspaper quoted documents provided by Edward Snowden, the former NSA contractor who fled to Russia earlier this year.

It said the documents showed that "the spy agency began allowing the analysis of phone call and email logs in November 2010 to examine Americans' networks of associations for foreign intelligence purposes after NSA officials lifted restrictions on the practice."

The policy shift was intended to help the agency "discover and track" connections between intelligence targets overseas and people in the United States, according to an NSA memorandum from January 2011, the Times said.

It said the NSA was authorized to conduct "large-scale graph analysis on very large sets of communications metadata without having to check foreignness" of every email address, phone number or other identifier, the document said. Because of concerns about infringing on the privacy of American citizens, the computer analysis of such data had previously been permitted only for foreigners.

The agency could augment the communications data with material from public, commercial and other sources, including bank codes, insurance information, Facebook profiles, passenger manifests, voter registration rolls and GPS location information, as well as property records and unspecified tax data, according to the documents, the paper said.

It said NSA officials declined to say how many Americans had been affected and said the documents did not describe the result of the scrutiny, which it said "links phone numbers and emails in a 'contact chain' tied directly or indirectly to a person or organization overseas that is of foreign intelligence interest."