China denied reports yesterday that its military had hacked into the US Defence Secretary’s computer system at a time of growing concern in the West about Beijing’s attempts to disrupt foreign computer networks.

The allegations mean that the US joins Britain and Germany in being the target of suspected Chinese cyber attacks.

The Pentagon acknowledged to The Times that earlier this year part of its computer system was temporarily shut down because of a “detected penetration”, but it refused to confirm or deny a report that the Chinese military had been behind the attack.

A shutdown of part of the House of Commons computer system last year could also have been the work of a Chinese gang, it was reported last night, with one expert saying that Chinese attacks on Whitehall computers were now a “constant ongoing problem”.

The concerns emerged a week after Angela Merkel, the German Chancellor, raised reports of Chinese infiltration of German government systems when she met Wen Jiabao, the Chinese Premier. Mr Wen said after their meeting: “We in the Government took [the reports] as a matter of grave concern.”

President Bush is due to meet Hu Jintao, the Chinese President, in Australia tomorrow. The two are in Sydney for the Apec summit. It is not known if Mr Bush will raise the allegations.

Responding to a report that the People’s Liberation Army hacked into a computer system in the office of Robert Gates, the US Defence Secretary, Jiang Yu, a Chinese Foreign Ministry spokeswoman, said: “Some people are making wild allegations against China. They are totally groundless and also reflect a Cold War mentality.

“We believe computer hacking is an international problem. China is also often the victim of hackers’ attacks. China has all along been opposed to and forbids criminal activities undermining computer networks. China is ready to strengthen cooperation with other countries, including the US, in countering internet crimes.”

The Pentagon said this year that Chinese military exercises in 2005 included hacking “primarily in first strikes against enemy networks”.

In July officials in the State Department said that large-scale hacking operations had penetrated computer systems in several parts of the world.

The hackers appeared to target the department headquarters and offices dealing with China and North Korea.

A Pentagon spokesman told The Times that a “number of nations and groups are actively developing” ways of hacking into its computer system. “We have seen attempts by a variety of state and non-state-sponsored organisations to gain unauthorised access to, or otherwise degrade, Department of Defence information systems.”

However, computer experts said that China had a large number of insecure computers and networks that hackers in other countries could use to disguise their locations and launch attacks.

In a separate development Ms Jiang denied a report that Chinese-made weapons had been used by Taleban fighters in Afghanistan.

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