"The information acquired has been part of an overall strategy to protect the United States from terrorist threats," National Intelligence Director James R Clapper said today.
In a statement, Clapper said the recordings "may assist counterterrorism personnel to discover whether known or suspected terrorists have been in contact with other persons who may be engaged in terrorist activities."
Clapper's statement came in response to reports appearing in several media outlets - The Washington Post and Guardian - that the US intelligence agencies have been secretly taking information on foreigners overseas for years from companies like Google, Facebook and Apple in search of security threats.
"We strongly object to using that power in this manner," The New York Times said in an editorial. "The administration has now lost all credibility. Mr. Obama is proving the truism that the executive will use any power it is given and very likely abuse it," the daily said.
In a report, The Washington Post said under the programme codenamed PRISM, the National Security Agency and the FBI are tapping directly into the central servers of nine leading US Internet companies - Microsoft, Yahoo, Google, Facebook, PalTalk, AOL, Skype, YouTube, Apple - extracting audio and video chats, photographs, e-mails, documents, and connection logs that enable analysts to track foreign targets.
"The court-approved programme is focused on foreign communications traffic, which often flows through US servers even when sent from one overseas location to another."
The companies, however, denied such allegations, arguing that they are not providing any such assistance to the US government.
"We have never heard of PRISM. We do not provide any government agency with direct access to our servers, and any government agency requesting customer data must get a court order," Apple spokesman Steve Dowling said.
In his statement, Clapper said: "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.
"The unauthorised disclosure of information about this important and entirely legal program is reprehensible and risks important protections for the security of Americans."