The US has charged five Chinese military officials in Beijing with economic espionage and trade secret theft.

The indictment accuses the five hackers of targeting US nuclear power, metals and solar products industries.

Six American companies, including Alcoa and Westinghouse, and one labour union were cited as victims of the hacking attacks.

Attorney General Eric Holder said the case "represents the first ever charges against a state actor for this type of hacking".

"The range of trade secrets and other sensitive business information stolen in this case is significant and demands an aggressive response," he told a news conference.

Barack Obama and Xi Jinping have discussed cyber-security issues

Mr Holder called the indictment a "ground-breaking" step forward in addressing the threat of cyber-security.

"For too long, the Chinese government has blatantly sought to use cyber espionage to obtain economic advantage for its state-owned industries," said FBI Director James Comey.

The US believes China stole military trade secrets costing American businesses billions of dollars a year.

Sky News Correspondent Dominic Waghorn in Washington says the charges are "unprecedented".

Last September, President Barack Obama discussed cyber-security issues with his Chinese counterpart Xi Jinping when the two met on the sidelines of a summit in St Petersburg, Russia.