NSA broke court’s rules on phone record surveillance

US intelligence officials have released secret documents showing that a judge reprimanded the National Security Agency in 2009 for violating its own procedures and misleading the nation's intelligence court about how it used the telephone call logs that it gathers.

It was the second severe scolding of the spy agency by the Foreign Intelligence Surveillance Court (FISC) to come to light since the disclosure of thousands of NSA documents by Edward Snowden, a former NSA contractor, began this summer.

The newly disclosed violations involved the NSA programme that has drawn perhaps the sharpest criticism from members of Congress and civil libertarians - the collection and storage for five years of information on virtually every phone call in the United States.

The agency uses orders from the intelligence court to compel phone companies to turn over records of numbers called and the time and duration of each call - the "metadata", but not the actual content of the calls.

Since Snowden disclosed the programme, the agency has said that while it gathers data on billions of calls, it makes only a few hundred queries in the database each year, when it has "reasonable, articulable suspicion" that a telephone number is connected to "terrorism".

But the new documents, released on Tuesday, show the agency also compares each day's phone call data as it arrives with an "alert list" of thousands of domestic and foreign phone numbers it has identified as possibly linked to "terrorism".