The United States National Security Agency collects hundreds of millions of contact lists from personal e-mail and instant messaging accounts around the world, including many from the US, The Washington Post reported on Monday.

The collection program intercepts e-mail address books and "buddy lists" from instant messaging services as they move across global data links, the newspaper said in an article posted on its website, citing senior intelligence officials and documents provided by former NSA contractor Edward Snowden.

It was the latest revelation of the spy agency's practices to be disclosed by Snowden.

The Post said analyzing that data lets the NSA search for connections and map relationships among foreign intelligence targets.

The data is collected outside the US but sweeps in the contacts of many US citizens, the report said, citing two senior US intelligence officials.

Shawn Turner, a spokesman for the Office of the Director of National Intelligence, which oversees the NSA, said the agency is focused on discovering and developing intelligence about foreign intelligence targets.

"We are not interested in personal information about ordinary Americans," Turner told the Post.

Turner said the NSA was guided by rules that require it to "minimize the acquisition, use and dissemination" of information that identifies US citizens or permanent residents.

The spy agency obtains the contact lists through secret arrangements with foreign telecommunications companies or other services that control Internet traffic, the Post reported.

Earlier this year, Snowden gave documents to the Post and The Guardian in the United Kingdom, disclosing US surveillance programs that collect vast amounts of phone records and online data in the name of foreign intelligence, often sweeping up information on US citizens.

The collection of contact lists in bulk would be illegal if done in the US, but the Post said the agency can get around that restriction by intercepting lists from access points around the world.

The newspaper quoted a senior intelligence official as saying NSA analysts may not search or distribute information from the contacts database unless they can "make the case that something in there is a valid foreign intelligence target in and of itself".

Commenting on the Post story, Alex Abdo, a staff attorney with the American Civil Liberties Union, said in an e-mailed statement: "This revelation further confirms that the NSA has relied on the pretense of 'foreign intelligence gathering' to sweep up an extraordinary amount of information about everyday Americans. The NSA's indiscriminate collection of information about innocent people can't be justified on security grounds, and it presents a serious threat to civil liberties."

Snowden's revelations about the reach and methods of the NSA, including the monitoring of vast volumes of Internet traffic and phone records, have upset US allies, from Germany to Brazil. Admirers call him a human rights champion and critics denounce him as a traitor.

The 30-year-old is now living in a secret location in Russia, beyond the reach of US authorities who want to prosecute him on espionage charges because he leaked the details of top-secret electronic spying programs to the media.

Reuters-AP