WASHINGTON - China and the United States traded hacking charges on Sunday as Washington accused Beijing of stealing U.S. intellectual property and the Chinese authorities expressed concern over U.S. cyberattacks.

The back-and-forth between the United States and China over cyber spying followed new claims by former National Security Agency contractor Edward Snowden that the U.S. spy agency was snooping on Chinese targets.

Snowden told Hong Kong's Sunday Morning Post that U.S. spies had hacked the prestigious Tsinghua University in Beijing — home to one of six "network backbones" that route all of mainland China's Internet traffic — and the Hong Kong headquarters of Pacnet, which operates one of the Asia-Pacific region's largest fiber-optic networks.

Snowden, who arrived in Moscow on Sunday, reportedly on his way to Venezuela, also said the U.S. spy agency was hacking Chinese mobile phone companies to gather data from millions of text messages.

NSA chief Keith Alexander, asked by ABC television if his agency carries out such activities as hacking Chinese cellphones to steal SMS messages, said "we have interest in those who collect on us as an intelligence agency.

"But to say that we're willfully just collecting all sorts of data would give you the impression that we're just trying to canvass the whole world," he said.

"The fact is what we're trying to do is get the information our nation needs, the foreign intelligence," Alexander said. "That's what you'd expect us to do. We do that right."

Asked if the United States was "losing the cyber war to China," Alexander said: "Our nation has been significantly impacted with intellectual property, the theft of intellectual property by China and others.

"That is the most significant transfer of wealth in history."