Google has expressed outrage in response to reports that the US National Security Agency intercepted communication links carrying its users' data.
The documents suggest the NSA worked with UK intelligence agency GCHQ to copy large amounts of user data transmitted over the fibre-optic link through an interception point outside the US.
The paper said by collecting the data outside the US, the NSA was able to circumvent the legal restrictions that prevent it from accessing the communications of people who live in the US.
According to a leaked document dated 9 January 2013, millions of records a day are sent from Yahoo and Google internal networks to NSA data warehouses.
The types of information sent ranged from metadata about who sent or received emails, the subject line and where and when, to content such as text, audio and video.
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Google's chief legal officer, David Drummond, said in a statement that the company was "outraged" by the latest revelations.
"We have long been concerned about the possibility of this kind of snooping, which is why we have continued to extend encryption across more and more Google services and links,” he said.
“We are outraged at the lengths to which the government seems to have gone to intercept data from our private fiber networks, and it underscores the need for urgent reform," said Drummond.
Yahoo joined Google in reiterating denials that they have ever provided any government with access to their systems.
Despite the data protection systems the companies have in place, the leaked documents suggest the NSA is able to bypass these controls.
However, a statement by the NSA in response to the reports denied circumventing limitations on domestic spying and reiterated denials of collecting vast quantities of US citizens’ data.
"NSA is a foreign intelligence agency. And we're focused on discovering and developing intelligence about valid foreign intelligence targets only," the statement said.
A spokesman for GCHQ declined to comment, according to the Guardian.
The latest allegations are likely to increase strain on relations between the US government and top technology companies who have been at pains to downplay claims of collaboration with the NSA.
Google, Yahoo and other tech companies have been calling for greater transparency over US government data requests since Snowden’s revelation of the NSA’s internet surveillance programme.