WASHINGTON (AFP) - The top US intelligence chief is seeking a criminal probe into bombshell leaks of US monitoring of Internet users and phone records, amid a furor over the secret programs' threat to privacy.
Director of National Intelligence James Clapper confirmed on Saturday that US spy agencies use a system called "PRISM" to gather data trails left by targeted foreign citizens using the Internet outside the United States.
But in an interview with NBC News, portions of which aired on Sunday, he called the disclosures "literally gut-wrenching" and said they had caused "huge, grave damage" to US intelligence capabilities.
"The NSA has filed a crimes report on this already," Clapper told NBC, referring to the leaks to the Guardian and The Washington Post.
He said he was "profoundly offended" that a disgruntled intelligence officer was a source for the leak to The Washington Post.
"This is someone who for whatever reason has chosen to violate a sacred trust for this country," he said.
"And, so, I hope we're able to track down whoever's doing this, because it is extremely damaging to, and it affects the safety and security of this country."
One top US lawmaker, Pete King, chairman of the House Subcommittee on Counterterrorism and Intelligence, in a statement on Sunday called for Snowden's extradition to the United States, saying he must be prosecuted "to the fullest extent of the law."
Glenn Greenwald, the Guardian reporter who brought to light the PRISM program and a separate program the scoops up US phone records, said the public had a right to know and openly debate what the government was doing.
"Every time there's a whistle blower, someone who exposes government wrongdoing, the tactic is to demonise them as a traitor," he said on ABC's "This Week."
"What they were seen being done in secret, inside the United States government, is so alarming they simply want one thing. And that is, they want the American people to learn about this massive spying apparatus and what the capabilities are, so we can have an open, honest debate."
Clapper said he understood public concerns about the invasion of privacy and threats to civil liberties, but said "a lot of what people are seeing and reading in the media is a lot of hyperbole."
The intelligence chief on Saturday declassified some details of the PRISM program in the face of a storm of controversy over suggestions that the government had a back door access to the servers of Internet giants like Google, Facebook and Yahoo! "PRISM is not an undisclosed collection or data mining program," he said.
"It is an internal government computer system to facilitate the government's statutorily authorised collection of foreign intelligence information from electronic communication service providers under court supervision."
The Internet service providers insisted they had not given direct access to customer data.
"Press reports that suggest that Google is providing open-ended access to our users' data are false, period," Google's CEO Larry Page and chief legal officer David Drummond said in a message on their official company blog.
"We provide user data to governments only in accordance with the law," they said.
Facebook founder Mark Zuckerberg described the press reports as "outrageous," insisting that his firm only provided user information to the authorities when compelled to by law. Yahoo! issued a similar denial.
Under PRISM, which has been running for six years, the US National Security Agency can issue directives to Internet firms demanding access to emails, online chats, pictures, files, videos and more uploaded by foreign users.
But Clapper's statement described a system whereby the government must apply to a secret US court for permission to target individuals or entities then issue a request to the service provider.
"The government cannot target anyone under the court approved procedures... unless there is an appropriate, and documented, foreign intelligence purpose for the acquisition," Clapper said.
Such a purpose, he continued, could be "the prevention of terrorism, hostile cyber activities or nuclear proliferation."
He admitted that data on US citizens might be "incidentally intercepted" in the course of targeting a foreign national, but said this would not normally be shared within the intelligence community unless it confirmed a threat.
PRISM was revealed shortly after The Guardian uncovered another intelligence program under which the NSA hoovered up the telephone records of millions of US citizens from the private telecoms provider Verizon.
Obama has defended the phone and Internet data trawls as a "modest encroachment" on privacy needed to keep Americans safe from terrorism.
But civil liberties and privacy groups have raised alarm at both programs, which some have branded "Orwellian" and possibly unconstitutional.
There have also been concerns abroad.
British opposition lawmakers have demanded an inquiry into a report the British signals intelligence agency GCHQ received PRISM data from its US ally and used it in reports.