Story highlights Director of national intelligence says the reports have "numerous inaccuracies"

He stresses that, per the law, U.S. citizens and people in U.S. can't be targeted

Washington Post, Guardian report U.S. agencies tapped the servers of tech giants

Facebook, Apple, others say they don't allow direct access to their servers

America's top intelligence official on Thursday night challenged news reports claiming Facebook posts, Gmail messages and more have been intercepted for years in a vast data-mining operation, saying the reports "contain numerous inaccuracies."

The Guardian , a British newspaper, and the Washington Post reported Thursday that U.S. intelligence agencies had access to the central servers of nine of the country's biggest technology firms including Microsoft, Apple, Google, Yahoo and Facebook.

The Post reported the program -- called PRISM -- underwent "exponential growth" since its founding in 2007. In fact, the newspaper said the program has become the leading source of raw material for the National Security Agency, the secretive U.S. intelligence operation that monitors electronic communications.

Yet several tech giants whose servers were reportedly ensnared in the program denied any knowledge of it Thursday.

Photos: Reports: Slides outline data-mining program Photos: Reports: Slides outline data-mining program Reports: Slides outline data-mining program – U.S. intelligence agencies operated a broad data-mining program that extracted e-mail, photos and other private communications from some of the biggest Internet companies, The Guardian and The Washington Post reported on Thursday, June 6. Hide Caption 1 of 4 Photos: Reports: Slides outline data-mining program Reports: Slides outline data-mining program – The Washington Post said it had been provided a detailed briefing presentation document on the program, called PRISM. This slide explains how international traffic is intercepted as it passes through the United States. Hide Caption 2 of 4 Photos: Reports: Slides outline data-mining program Reports: Slides outline data-mining program – The intelligence agencies reportedly have access to the central servers of nine major firms, including Microsoft, Apple, Google, Yahoo and Facebook. The information they can collect varies by provider. Hide Caption 3 of 4 Photos: Reports: Slides outline data-mining program Reports: Slides outline data-mining program – The program has been running since 2007 and has undergone "exponential growth" since then, The Washington Post reported. Hide Caption 4 of 4

And James Clapper, the director of national intelligence, questioned the Guardian and Post articles in a statement Thursday night.

He referred to Section 702 of the Foreign Intelligence Surveillance Act, which he noted was recently reauthorized by Congress -- one of the bodies, along with the executive branch and Foreign Intelligence Surveillance Court, with oversight over aspects of intelligence gathering.

Section 702, Clapper added, "is designed to facilitate the acquisition of foreign intelligence information concerning non-U.S. persons located outside the United States."

"It cannot be used to intentionally target any U.S. citizen, any other U.S. person, or anyone located within the United States," he said in his statement.

While he made no mention of data mining, Clapper did defend the American intelligence effort generally, saying, "Information collected under this program 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."

Clapper also called out the person or people behind "the unauthorized disclosure of information about this important and entirely legal program," saying such apparent leaks are "reprehensible and risks important protections for the security of Americans."

The Post reported that its reporters had been provided a detailed briefing presentation document on the PRISM program.

The program has been running since 2007 and has undergone "exponential growth" since then, the Post reported. It is now the leading source of raw material for the National Security Agency, the secretive U.S. intelligence operation that monitors electronic communications.

According to a briefing slide published by the Guardian, PRISM began with data from Microsoft in 2007. The program began collecting data from Yahoo in 2008 and from Google, Facebook and the message system PalTalk in 2009. YouTube became a source in 2010, Skype and AOL in 2011 and Apple in late 2012, the slide claims.

The NSA declined to comment, but several companies -- many of them using similar language -- denied Thursday any knowledge of such a program.

Microsoft, for instance, said in a statement it only provides user data when legally required and for specific accounts -- adding that "if the government has a broader voluntary national security program to gather customer data we don't participate in it."

Jodi Seth, a spokeswoman for Facebook, said the social media giant works to "carefully scrutinize any ... request for compliance" and does not give government agencies "direct access" to its servers.

Apple spokesman Steve Dowling offered a similar response -- saying Apple hands over information only when a government agency gets a court order. Dowling added that his company has never heard of PRISM.

"We disclose user data to government in accordance with the law, and we review all such requests carefully," a Google spokesman said in response to the stories. "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."

Even with these denials and Clapper's defense, President Barack Obama's administration has come under growing scrutiny in recent days over his record on balancing citizens' right to privacy and the government's efforts to combat terrorism.

That includes news, first reported on Wednesday by the Guardian and commented on by U.S. politicians, that the FBI and National Security Agency have been collecting the phone records of millions of Americans -- specifically Verizon customers and perhaps others -- over a several year period.

Days after taking office in 2009, Obama vowed , "Transparency and the rule of law will be the touchstones of this presidency." But on Thursday, the left-leaning Huffington Post conflated Obama with his predecessor George W. Bush while a New York Times editorial said "the administration has now lost all credibility" when it comes to overreaching in the name of fighting terrorism.

"Mr. Obama is proving the truism that the executive branch will use any power it is given and very likely abuse it," the Times' editorial said.