A 29-year-old American has outed himself as the source behind the biggest intelligence leak in the NSA's history.
Edward Snowden, who works as a contract employee at the National Security Agency, is the source of The Guardian's disclosures about the US government's secret surveillance programmes.
The leaks have reopened the post-Sept. 11, 2001, debate about privacy concerns versus heightened measures to protect against terrorist attacks, and led the NSA to ask the Justice Department to conduct a criminal investigation.
The Guardian said it was publishing the identity of Edward Snowden, a former technical assistant for the CIA and current employee of defence contractor Booz Allen Hamilton, at his own request.
"I have no intention of hiding who I am because I know I have done nothing wrong," Mr Snowden was quoted as saying.
The director of national intelligence, James Clapper, has decried the revelation of the intelligence-gathering programmes as reckless, and in the past days has taken the rare step of declassifying some details about them to respond to media reports about counterterrorism techniques employed by the government.
An Internet scouring program, code-named PRISM, allows the NSA and FBI to tap directly into the servers of major US internet companies such as Google, Apple, Microsoft, Facebook and AOL, scooping out emails, video chats, instant messages and more to track foreign nationals who are suspected of terrorism or espionage.
The NSA also is collecting the telephone records of millions of American customers, but not actual conversations.
President Barack Obama, Mr Clapper and others have said the programmes have been repeatedly authorised by Congress and are subject to strict supervision of a secret court.
Mr Snowden is quoted as saying that his "sole motive is to inform the public as to that which is done in their name and that which is done against them."
The Guardian reported that Mr Snowden was working in an NSA office in Hawaii when he copied the last of the documents he planned to disclose and told supervisors that he needed to be away for a few weeks to receive treatment for epilepsy.
He left for Hong Kong on May 20 and has remained there since, according to the newspaper. Mr Snowden is quoted as saying he chose that city because "they have a spirited commitment to free speech and the right of political dissent", and because he believed it was among the spots on the globe that could and would resist the dictates of the US government.
Mr Snowden is quoted as saying he hopes the publicity the leaks have caused will provide him some protection and that he sees asylum, perhaps in Iceland, as a possibility.
"I feel satisfied that this was all worth it. I have no regrets," Mr Snowden told the newspaper.
He was said to have worked on IT security for the CIA and by 2007, was stationed with diplomatic cover in Geneva, responsible for maintaining computer network security. That gave him clearance to a range of classified documents, according to the report.
"Much of what I saw in Geneva really disillusioned me about how my government functions and what its impact is in the world," he says. "I realised that I was part of something that was doing far more harm than good."
Meanwhile British Foreign Secretary William Hague has insisted the UK Government Communications Headquarters (GCHQ) has not been using PRISM to dodge tough legal checks on their activities.
He refused to confirm or deny details of the eavesdropping agency's links to the Prism spy scheme, but said the law-abiding British public had "nothing to fear" from their work.
Mr Hague said: "As someone who knows GCHQ very well... the idea that in GCHQ people are sitting working out how to circumvent a UK law with another agency in another country is fanciful. It is nonsense."
The row crossed the Atlantic after The Guardian said it had seen documents showing that GCHQ had access to the Prism system since at least June 2010.
The British agency, based at Cheltenham, was said to have generated 197 intelligence reports through the system in the 12 months to May 2012 - a 137% increase on the previous year.
According to the newspaper, the Prism programme appeared to allow GCHQ to circumvent the formal legal process required to obtain personal material, such as emails, photographs and videos, from internet companies based outside the UK.
GCHQ refused to comment directly on the report, but in a statement it insisted that it operated within a "strict legal and policy framework".