Internet giant Google says that it is "outraged" at the possibility that US intelligence agencies have secretly broken into the main communications links that connect Google and Yahoo data centres around the world, as reported by the Washington Post.
The Post published a report on Wednesday indicating that the National Security Agency (NSA) had obtained access to the main data lines for both companies, citing documents obtained by former NSA contractor Edward Snowden.
A secret document dated January 9 indicates that National Security Agency sends millions of records every day from Yahoo and Google internal networks to data warehouses at the agency's Fort Meade, Maryland headquarters, the Post reported.
We do not provide any government, including the US government, with access to our systems.
During the past month, field collectors had processed and sent back more than 180 million new records ranging from "metadata", which would indicate who sent or received emails and when, to content such as text, audio and video, according to the newspaper.
David Drummond, Google's chief legal officer, said the company had "long been concerned about the possibility of this kind of snooping".
"We do not provide any government, including the US government, with access to our systems," Drummond said.
"We are outraged at the lengths to which the government seems to have gone to intercept data from our private fibre networks, and it underscores the need for urgent reform."
Google, which is known for its data security, noted that it has been trying to extend encryption across more and more Google services and links.
Senate to limit NSA access
The new details about the NSA's access to Yahoo and Google data centres come at a time when Congress is reconsidering the government's collection practices and authority.
Leaders of a US Senate panel that oversees US intelligence issues said on Thursday that they had approved a plan to scale back how many US telephone records the NSA was allowed to access.
But critics of US surveillance programmes and privacy rights experts said the bill does little, if anything, to end the daily collection of millions of records that has spurred widespread demands for reform.
Legislation by the Senate Intelligence Committee, which was approved by an 11-4 vote, would increase congressional and judicial oversight of intelligence activities. It also would create 10-year prison sentences for people who access the classified material without authorisation, according to a statement released by committee chairwoman Dianne Feinstein, a Democrat, and Saxby Chambliss, the panel's top Republican.
Earlier this week, US President Barack Obama said he had ordered a review of the way US spy agencies gather intelligence after it emerged that millions of phone calls in Europe were bugged, including German Chancellor Angela Merkel.
France, Germany and Spain are some of the countries now seeking explanations.
An Italian magazine Panorama claimed on Wednesday that the NSA allegedly eavesdropped on cardinals before the conclave in March to elect a new pope.
"Although there's a diminished standard of legal protection for interception that occurs overseas, the fact that it was directed apparently to Google's cloud and Yahoo's cloud, and that there was no legal order as best we can tell to permit the interception, there is a good argument to make that the NSA has engaged in unlawful surveillance," said Marc Rotenberg, executive director of Electronic Privacy Information Center.
The reference to 'clouds' refers to sites where the companies collect data.
But speaking to Bloomberg News on Wednesday, NSA Director General Keith Alexander denied his organisation had infiltrated Yahoo and Google databases.
"Not to my knowledge," said Alexander.
"We are not authorised to go into a US company's servers and take data. We'd have to go through a court process for doing that."
Congress members and international leaders have become increasingly angry about the NSA's data collection, as more information about the programmes leak out.
Alexander told lawmakers that the US did not collect European records, and instead the US was given data by NATO partners as part of a programme to protect military interests.
He defended the overall NSA effort to monitor communications. Pointing to thousands of terror attacks around the world, he said that the US has been spared much of that violence because of such programmes.