Europeans spy just as much, US intelligence chiefs say

General Keith Alexander, head of the National Security Agency (NSA), said the media reports were based on a misunderstanding of information passed by Snowden to European newspapers.

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

He said it was not the NSA collecting so-called metadata, details about who made a phone call and when, hinting it was European intelligence services who did it in their respective countries.

"They cite as evidence screen shots of the results of a web tool used for data management purposes, but both they and the person who stole the classified data did not understand what they were looking at," he said.

Dianne Feinstein, a senator chairing the intelligence committee, backed up his claims.

"This was not the United States collecting on France and Germany. This was France and Germany collecting. And it had nothing to do with their citizens, it had to do with collecting in Nato areas of war, like Afghanistan," she said.

As for spying on leaders, Obama's chief intelligence adviser, James Clapper, said it is a commonplace in foreign espionage.

"That's a hardy perennial," Clapper said.

"It's one of the first things I learned in intel school in 1963, that this is the fundamental given in the intelligence business is leadership intentions, no matter what level you're talking about," he added.

Meanwhile, Spanish prosecutors have opened a preliminary investigation into the NSA mass surveillance.

German prosecutors looking at the Merkel phone affair are taking similar steps.