James Clapper, the director of US national intelligence, has reacted sharply after leaked documents revealed information about two top-secret intelligence-gathering programmes.
In an unusual statement late on Thursday, Clapper called disclosure of the internet surveillance program "reprehensible" and said the leak about the phone record collecting could cause long-lasting and irreversible harm to the nation's ability to respond to threats.
Clapper said news reports about the programmes contained inaccuracies and omitted key information. He declassified some details about the authority used in the phone records programme because he said Americans must know the programme's limits.
Those details included that a special national security court reviews the programme every 90 days and that the court prohibits the government from indiscriminately sifting through phone data. Queries are only allowed when facts support reasonable suspicion, Clapper said.
After reports of surveillance of phone records, the Washington Post and The Guardian reported on Thursday the existence of another programme used by the NSA and FBI that scours the nation's main internet companies, extracting audio, video, photographs, emails, documents and connection logs to help analysts track a person's movements and contacts.
It was not clear whether the programme, called Prism, targets known suspects or broadly collects data from other Americans.
The companies include Microsoft, Yahoo, Google, Facebook, PalTalk, AOL, Skype, YouTube and Apple. The Post said PalTalk has had numerous posts about the Arab Spring and the Syrian civil war. It also said Dropbox would soon be included.
Google, Facebook and Yahoo said in statements that they do not provide the government with direct access to their records. In a statement, Google said it discloses user data to the government in accordance with the law and reviews all such requests carefully. "From time to time, people allege that we have created a government 'back door' into our systems, but Google does not have a 'back door' for the government to access private user data," the statement said.
Earlier, a leaked document laid bare the monumental scope of the US government's surveillance of Americans' phone records — hundreds of millions of calls — in the first hard evidence of a massive data collection program aimed at combating terrorism under powers granted by Congress after the 9/11 attacks in 2001.
At issue is a court order, first disclosed on Wednesday by The Guardian in Britain, which requires communications company Verizon to turn over the records of all landline and mobile telephone calls of its customers on an "ongoing, daily basis", both within the US and between the US and other countries.
Intelligence experts said the government, though not listening in on calls, would be looking for patterns that could lead to terrorists — and that there was every reason to believe similar orders were in place for other phone companies.
Some critics in Congress, as well as civil liberties advocates, declared that the sweeping nature of the National Security Agency program represented an unwarranted intrusion into Americans' private lives. But a number of lawmakers, including some Republicans who normally jump at the chance to criticize the Obama administration, praised the programme's effectiveness. Leaders of the House Intelligence Committee said the program had helped thwart at least one attempted terrorist attack in the United States.