Washington: The US National Security Agency has created a surveillance system that is recording all the phone calls in an undisclosed foreign country, allowing it to play back any conversation up to 30 days later, the Washington Post reported on Tuesday.

The newspaper cited unnamed sources with direct knowledge of the system as well as documents supplied by former NSA contractor Edward Snowden, who since last year has leaked extensive data revealing sweeping US spying activities.

The newspaper said that at the request of US officials, it was withholding details that could be used to identify the nation where the system is being used or others where it might be used in the future. The Post cited documents that envisioned similar US spying operations in other nations.

Mr Snowden again spoke from his Russian exile on Tuesday, addressing a conference audience in Vancouver through a screen and a remote-controlled robot.

Advertisement

"There are absolutely more revelations to come," he said. "Some of the most important reporting to be done is yet to come."

The voice interception program is known as MYSTIC and started in 2009, with its "retrospective retrieval" capability, called RETRO, reaching full strength in 2011 against the first target nation.

A classified summary of the system said the collection effort was recording "every single" conversation nationwide in the first target country, storing billions of conversations in a 30-day rolling buffer that clears out the oldest calls as new ones are made.

A senior manager for the program likened it to a time machine that can replay voices from any phone call without the need to identify a person for spying in advance.

Current and former US officials quoted anonymously said large numbers of conversations involving Americans would be gathered using the system.

See more here:

NSA records all calls in targeted foreign nation :report