US public concerns about government have widened with the revelation that the National Security Agency (NSA) and the FBI are tapping directly into the servers of nine US internet companies.
The news follows evidence that the NSA is collecting the phone records of millions of US citizens under a court order issued in terms of the US Patriot Act.
In the latest development, it has emerged that the NSA has obtained access to the systems of top internet companies as part of a previously undisclosed programme called Prism.
The programme has enabled the NSA and FBI to extract audio and video chats, photographs, e-mails, documents, and connection logs to track foreign targets, according The Washington Post.
Analysts are able to pull out material that matches a set a selectors or search terms from the data streams of the companies named in a document obtained by the paper.
Prism was reportedly developed in 2007 out of a programme of domestic surveillance without warrants set up by president George W. Bush, following the 2001 World Trade Center attack.
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US national intelligence director James Clapper has admitted the government collects communications from internet firms, but said reports by The Washington Post and The Guardian about Prism contained "numerous inaccuracies", although he did not offer any details.
In a statement, Clapper said Prism was "designed to facilitate the acquisition of foreign intelligence information concerning non-US persons located outside the United States".
"It cannot be used to intentionally target any US citizen, any other US person, or anyone located within the United States," he added.
Clapper said the programme, under Section 702 of the Foreign Intelligence Surveillance Act, was recently re-authorised by Congress after hearings and debate.
"Information collected under this programme is among the most important and valuable foreign intelligence information we collect and is used to protect our nation from a wide variety of threats," he said.
Although US citizens are not the intended target of Prism, the Washington Post said content from Americans is still screened to track or learn more about the target.
The data gathered through Prism has grown to become a major contributor to the president's daily briefing and accounts for almost one in seven intelligence reports, it adds.
The Washington Post named the nine companies taking part in Prism as Google, Facebook, Apple, Microsoft, Yahoo, PalTalk, AOL, Skype and YouTube.
Many of the companies have denied giving government agents direct access to their central servers.
Microsoft told the BBC that it turned over customer data only when given a legally binding order and complied with orders only for specific accounts.
"If the government has a broader voluntary national security programme to gather customer data, we don't participate in it," Microsoft said.
Google, Yahoo, Apple and Facebook have all issued statements saying they did not give the government direct access to their servers.