The robust Chinese response followed a front-page report in the Financial Times saying Chinese People's Liberation Army (PLA) hackers broke into a US defence department network in June, taking data and causing the shutdown of a system serving the secretary of defence, Robert Gates.

"The Chinese government has consistently opposed and vigorously attacked according to the law all internet-wrecking crimes, including hacking," the foreign ministry spokeswoman Jiang Yu was quoted by Reuters as saying.

"Some people are making wild accusations against China... These are totally groundless and also reflect a cold war mentality."

According to the FT, a senior US official said the Pentagon had pinpointed the exact origin of the attack. Another official told the paper there was a "very high level of confidence... trending towards certainty" that the PLA was responsible.

The paper quoted a former US official as saying the PLA was able to disrupt and even disable the Pentagon's computer system. "The PLA has demonstrated the ability to conduct attacks that disable our system... and the ability in a conflict situation to re-enter and disrupt on a very large scale," the former official told the FT.

The German chancellor, Angela Merkel, has raised similar concerns about Chinese hackers infecting German government ministries with spying programs.

In the attack against the Pentagon, the FT said, hackers from several locations in China spent several months probing the Pentagon system before overcoming its defences. The Pentagon was forced to take down the network for more than a week during the attacks.

"There are multiple wake-up calls stirring us to levels of more aggressive vigilance," Richard Lawless, the Pentagon's top Asia official, told the FT at the time.

The report comes as the US president, George Bush, is to meet Hu Jintao, the Chinese president, tomorrow in advance of the Apec summit of Pacific rim leaders.

In May, the small Baltic country of Estonia was subjected to a three-week wave of hacking that disabled websites of government ministries, political parties, newspapers, banks and companies.

The attacks led to Nato urgently examining the offensive and its implications. They came amid a row over Estonia's removal of the "bronze soldier" Soviet war memorial in central Tallinn. The issue brought relations between Russia and Estonia to their lowest ebb since the collapse of the Soviet Union.