WASHINGTON (Reuters) - A U.S. intelligence agency requested a criminal probe on Saturday into the leak of highly classified information about secret surveillance programs run by the National Security Agency, a spokesman for the intelligence chief's office said.

Confirmation that the NSA filed a "crimes report" came a few hours after the nation's spy chief, Director of National Intelligence James Clapper launched an aggressive defense of a secret government data collection program.

Clapper blasted what he called "reckless disclosures" of a highly classified spy agency project code-named PRISM.

It was not known how broad a leaks investigation was requested by the super-secret NSA, but Shawn Turner, a spokesman for Clapper's office, said a "crimes report has been filed."

The report goes to the Justice Department, which has established procedures for determining whether an investigation is warranted. Prosecutors do not accept all requests, but they have brought a series of high-profile leak investigations under President Barack Obama. U.S. officials said the NSA leaks were so astonishing they expected the Justice Department to take the case.

A Justice Department spokesman declined to comment.

In a statement earlier on Saturday, Clapper acknowledged PRISM's existence by name for the first time and said it had been mischaracterized by the media. The project was legal, not aimed at U.S. citizens and had thwarted threats against the country, he said.

"Over the last week we have seen reckless disclosures of intelligence community measures used to keep Americans safe," Clapper said in a statement.

He said the surveillance activities reported in the Washington Post and Britain's Guardian newspaper were lawful and conducted under authorities approved by Congress. "Significant misimpressions" have resulted from recent articles, he said.

ESCALATING BATTLE

Clapper's comments were the latest development in an escalating battle over government spying and civil liberties, involving the Obama administration and news organizations that have published details of U.S. data-mining efforts.

Clapper's statement discussed in general terms what had been until Thursday an unknown and highly classified program. It made a rare public acknowledgement that U.S. spy agencies obtained data from U.S. telecommunications providers, but defended the practice as legal and regulated by courts.

"The United States Government does not unilaterally obtain information from the servers of U.S. electronic communication service providers. All such information is obtained with FISA Court approval and with the knowledge of the provider," said a fact sheet accompanying Clapper's statement, referring to the Foreign Intelligence Surveillance Act Court.

PRISM, characterized in news reports as a top-secret National Security Agency program for extracting data from the computers of internet companies, in reality is an "internal government computer system" used to "facilitate" the government's handling of information it collects from service providers, according to the fact sheet.

The reports this week said the surveillance program involving internet firms and established under Republican President George W. Bush in 2007, had seen "exponential growth" under Obama, a Democrat. It said the NSA increasingly relied on PRISM as a source of raw material for daily intelligence reports to the president.

The news reports included PowerPoint slides showing that major Internet companies such as Yahoo, Google, Facebook and a half-dozen others were involved in the program.

Alan Rusbridger, editor-in-chief of the Guardian, had no comment on Clapper's statement. Washington Post spokeswoman Kris Coratti said the company had no comment.

'APPROPRIATE FOREIGN INTELLIGENCE PURPOSE'

Internet providers have said they knew nothing about any NSA collection program called PRISM and that they have only cooperated with legal government requests for data.

The government can only target someone for internet surveillance if "there is an appropriate, and documented foreign intelligence purpose" for collection, the fact sheet said.

Those purposes include countering terrorism, weapons proliferation and cyber threats, Clapper said in the statement. He did not further explain how those broad targeting guidelines were used in practice.

Previous administration statements in the wake of leaks about the NSA program had not mentioned that it was gathering information related to cyber threats and weapons proliferation.

The Guardian published a story on Saturday, based on what it said were more leaked classified NSA documents, about what it described as an internal agency data mining tool created to track the focus of NSA's efforts to collect "metadata" - primitive raw information about message traffic - from around the world.

The newspaper said that a different NSA fact sheet it obtained said that the tool, code-named Boundless Informant, "allows users to select a country on a map and view the metadata volume and select details about the collections against that country."

The Guardian said documents showed NSA collected "almost 3 billion" pieces of intelligence from U.S. computer networks over a period ending in March 2013. It said the new documents raised questions about what NSA had told Congress about its inability to keep close track on the extent to which it inadvertently collects information about messages sent by Americans.

(Writing by David Ingram; Editing by Warren Strobel and Peter Cooney)