An analyst cited by Chinese state media has said the leaked US surveillance programme PRISM will likely test the already rocky relationship between Washington and Beijing amid revelations that the US has hacked into computers in China since 2009.

Shaky US-China relations could face further challenges in the wake of the whistleblowing scandal over the massive electronic surveillance programme PRISM by the US National Security Agency (NSA), Chinese state media said on Thursday.

Edward Snowden, a former spy-agency contractor who has caused a furore by exposing the top-secret programme to gather and analyse Internet and phone data, told Hong Kong’s South China Morning Post on Wednesday that there had been more than 61,000 NSA hacking operations globally.

Snowden also told the daily that the NSA has hacked computers in China and Hong Kong since 2009.

The leaks were meant to demonstrate "the hypocrisy of the US government when it claims that it does not target civilian infrastructure, unlike its adversaries," Snowden added.

Reacting to those revelations, Li Haidong, an analyst quoted in the state-run China Daily said the programme “is certain to stain Washington's overseas image and test developing Sino-US ties.”

Washington has repeatedly accused Beijing of cyber-spying, but President Barack Obama and his Chinese counterpart Xi Jinping adopted a conciliatory tone at a two-day summit in California last week.

“How the case is handled could pose a challenge to the burgeoning goodwill between Beijing and Washington given that Snowden is in Chinese territory and the Sino-US relationship is constantly soured on cybersecurity,” Haidong added.

Adding to the diplomatic complications, the rogue contractor Snowden has flown to the semi-autonomous Chinese city of Hong Kong and vowed to resist attempts to extradite him to the US.

On Thursday China said it had "no information to offer" on Snowden.

Parliamentary grilling scheduled

Meanwhile, National Security Agency chief General Keith Alexander, who is in charge of the leaked programme, defended the intelligence tactic on Wednesday, insisting it had helped thwart dozens of terror attacks.

Facing sceptical questions from lawmakers Alexander insisted the programme operates under proper legislative and judicial oversight.

"It's classified but it's dozens of terrorist events that these have helped prevent," he told the hearing, the first time he had been questioned in public since Snowden went public last week.

"I want the American people to know that we're being transparent in here," he insisted, warning that "the trust of the American people" was a "sacred requirement" if his agency was to be able to do its job.

Asked if the light shone on the programmes could help terrorists avoid surveillance, Alexander said: "They will get through, and Americans will die."

A new confidential briefing for the US Senate is set for Thursday to discuss details of the NSA surveillance.

(FRANCE 24 with wires)