A report published by the Washington Post newspaper details cases in which the NSA overstepped its authority or outright broke the law since 2008, when the agency was granted more extensive powers in exchange for increased oversight.

One of the documents is an NSA audit from May of 2012, which lists 2,776 incidents over the preceding 12 months, relating to the unauthorized collection, storage, access to or distribution of communications.

The report also cites one case of a violation of court order as well as the unauthorized use of data in more than 3,000 cases of American citizens or foreign legal residents of the country.

In another case, what is described as a "large number" of telephone calls placed from Washington were intercepted due to a programming error, which caused computers to mistake the US capital's 202 area code for 20, the international dialing code for Egypt.

According to the report, most of these violations were not deliberate, but were the result of a lack of due diligence on the part of NSA staffers.

"We're a human-run agency operating in a complex environment with a number of different regulatory regimes, so at times we find ourselves on the wrong side of the line," an NSA official speaking on condition of anonymity told the paper.

The paper said the documents, which it has posted on its website, were obtained from Edward Snowden, the former NSA subcontractor who US authorities want to put on trial on espionage charges. Russia granted Snowden temporary asylum earlier this month.

Snowden's revelations have raised concerns about the surveillance activities of not just the NSA but also other American and British intelligence agencies. Earlier this month, US President Barack Obama announced a number of measures meant to restore trust in US intelligence agencies, not only among the American public but among Washington's allies.

pfd/mz (AFP, AP, Reuter)