U.S. National Security Agency Director General Keith Alexander on Tuesday told lawmakers that the recent media reports about the agency's spying on European allies are "completely false."

Top U.S. intelligence officials testified before the U.S. Congress, the first of its kind following recent media disclosures about U.S. spying on European allies, including millions of citizens in France and Spain and Germany Chancellor Angela Merkel.

"The assertions by reporters in France, Spain, Italy that NSA collected tens of millions of phone calls are completely false," said Alexander at a House Intelligence Committee hearing.

The NSA chief said such data in question came from foreign intelligence agencies and was usually gathered outside Europe.

"This is not information that we collected on European citizens, " he said, adding that the European media has misinterpreted the classified documents leaked by former U.S. defense contractor Edward Snowden.

Instead, the information represented information that the U.S. and its NATO allies have collected "in defense of our countries," he said.

Speaking at the same hearing, U.S. Director of National Intelligence James Clapper said the NSA and the U.S. intelligence community do not spy indiscriminately on citizens of any country.

"We do not spy on anyone except for valid foreign intelligence purposes," he added.

The top intelligence official also warned Congress not to overreact to the media disclosures and thus undermine counter-terrorism programs.

"We must remain mindful of the potential impact of over- correcting the authorization of the intelligence community," he said.

American allies in Europe have been in an uproar over the media reports that U.S. intelligence agencies have monitored the communications of Merkel and tens of millions of phone calls in France and Spain.

U.S. Senate Intelligence Committee Chairwoman Dianne Feinstein, one of the defenders of the U.S. intelligence surveillance programs, announced that the panel will initiate "a major review" into all U.S. intelligence programs.