China's military says overseas computer hackers targeted two of its websites an average of 144,000 times per month last year, with almost two thirds of the attacks originating in the United States.

The comments by Defense Ministry spokesman Geng Yansheng on Thursday followed accusations last week by an American cybersecurity company that Chinese military-backed cyberspies infiltrated and stole massive amounts of data from U.S. companies and other entities. China denied the allegations and its military said it has never supported any hacking activity.

Geng told reporters at a monthly news conference that an average of 62.9 per cent of the attacks on the Defense Ministry's official website and that of its newspaper, the People's Liberation Army Daily, came from the U.S.

China says its military cyberforce is purely for defense.