This wanted poster is displayed at the Justice Department in Washington after Attorney General Eric Holder announced that a US grand jury has charged five Chinese hackers with economic espionage and trade secret theft.

Beijing -

China on Tuesday warned the United States was jeopardising military ties by charging five Chinese officers with cyberspying and tried to turn the table on Washington by calling it “the biggest attacker of China's cyberspace.”

China announced it was suspending co-operation with the United States in a joint cybersecurity task force over Monday's indictments, which accused the officers of stealing trade secrets from major American companies.

The testy exchange marked an escalation in tensions over US complaints that China's military uses its cyber warfare skills to steal foreign trade secrets to help the country's vast state-owned industrial sector. A US security firm, Mandiant, said last year it traced attacks on American and other companies to a military unit in Shanghai.

The charges are the biggest challenge to relations since a meeting last summer between President Barack Obama and his Chinese counterpart, Xi Jinping, in Sunnylands, California.

US-Chinese relations already were under strain from conflicts over what Washington says are provocative Chinese moves to assert claims over disputed areas of the East and South China Seas. Beijing complains the Obama administration's effort to shift foreign policy emphasis toward Asia and expand its military presence in the region is emboldening Japan and other neighbours and fuelling tension.

Beijing has denied conducting commercial spying and said it is a victim of computer hacking, but has given little indication it investigates foreign complaints.

“The US accusation against Chinese personnel is purely ungrounded and absurd,” said a statement carried by the official Xinhua News Agency and read on the state TV midday news.

The Foreign Ministry summoned American Ambassador Max Baucus on Monday night to receive a formal protest.

The Ministry of Defence warned that the US accusations would chill gradually warming relations between the two militaries.

“The United States, by this action, betrays its commitment to building healthy, stable, reliable military-to-military relations and causes serious damage to mutual trust,” it said.

Also on Tuesday, the Cabinet's Internet information agency said Chinese networks and websites have been the target of thousands of hacking attacks from computers in the United States.

“The US is the biggest attacker of China's cyber space,” Xinhua said, citing a statement by the agency. “The US attacks, infiltrates and taps Chinese networks belonging to governments, institutions, enterprises, universities and major communication backbone networks.”

Monday's indictment said the People's Liberation Army officers targeted US makers of nuclear and solar technology, stealing confidential business information, sensitive trade secrets and internal communications. The targets were Alcoa World Alumina, Westinghouse Electric Co, Allegheny Technologies, US Steel Corp, the United Steelworkers Union and SolarWorld.

The Justice Department said the charges should be a national “wake-up call” about cyber intrusions. American authorities have previously announced details of cyberattacks from China but Monday's indictment was the first accusation to name individuals.

In announcing the suspension of its work with the cybersecurity group, the Chinese government warned of further retaliation “as the situation evolves.”

The working group was established in April 2013, following the publication of allegations of spying by the Chinese military and held its first meeting last July.

The new indictment attempts to distinguish spying for national security purposes - which the US admits doing - from economic espionage intended to gain commercial advantage for private companies or industries.

The United States denies spying for commercial advantage, though documents released by former National Security Agency contractor Edward Snowden said the NSA broke into the computers of Brazil's main state-owned oil company, Petrobras. Brazilian President Dilma Rousseff said if that was true, then the motive would be to gather economic information.

The indictment says the Chinese hackers stole proprietary information from the companies and the labor union, including design specification for Westinghouse pipes and pricing and strategy information from SolarWorld.

Working from a building in Shanghai, prosecutors say, the hackers in some cases gained access to networks by sending emails to company employees that looked authentic but that actually contained a link to malicious code.

The defendants are believed to be in China and it was unclear whether any might ever be turned over to the US for prosecution. The Justice Department identified all five by name and issued wanted posters. - Sapa-AP