China's military spokesman said on Wednesday that the country's armed forces had never backed any hacking activities, denouncing US cyber security firm Mandiant's report as groundless both in facts and legal basis.

China's laws ban any activities disrupting cyber security and the Chinese government always cracks down on cyber crimes, Geng Yansheng, spokesman with the Ministry of National Defense, said at a briefing.

Mandiant on Monday released a report which alleged that a secret Chinese military unit in Shanghai was behind years of cyber attacks against US companies.

Geng said Mandiant's report was groundless in fact because it came to the conclusion that the source of attack came from China simply because of the discovery that attacks were linked to IP addresses based in China.

First, as known to all, it is so common for hacking attacks on the Internet to take place by peculating IP addresses that "it happens almost everyday," according to the spokesman.

Second, there has been no clear and consistent definition of cyber attacks around the world. The report lacks legal basis to assert cyber espionage only by cataloguing some routine cyber activities, he said.

Third, cyber attacks are transnational, anonymous and deceptive with their source often difficult to identify. Releasing irresponsible information will not help solve problems, Geng added.

The spokesman further said China actually is a major victim of cyber attacks.

Statistics show that Chinese military end users connected to the Internet frequently come under cyber attack from abroad. In these cases, source IP addresses suggest that the majority of them come from the United States, Geng said, adding, "but we do not point fingers at the United States based on the above-mentioned findings, and every country should deal with cyber security in a professional and responsible manner."

Additionally, he said, to address criticism from foreign statesmen and media outlets about Chinese hacking, the Chinese side would like to resolve the issues through joint law enforcement and consultations with other countries.

According to the spokesman, the Chinese Ministry of Public Security has assisted more than 50 countries and regions in investigating some 1,100 cases of cyber crime since 2004, and China has established bilateral law enforcement cooperation with over 30 nations and regions, including the United States, Britain, Germany and Russia.

Lodging one-sided media accusations will not help solve problems, but only jeopardize existing cooperation, he urged.

Jin Canrong, an American studies expert with Renmin University, said the real motive behind the US hacking accusation is to seek an upper hand in Sino-US relations.

It signalled that the US is looking for fresh topics over which to criticise China in a effort to achieve dominance, according to Jin. As the United States is losing its traditional superiority, the cards it can play are getting fewer and fewer, but accusing China of cyber attacks becomes a new one.

Against the backdrop of fiscal constraints, the US military fears cut-backs in military budgets, hence whipping up fear about new threats such as alleged cyber attacks from China, particularly when traditional security threats look less and less daunting, the academic said.

Furthermore, Jin added, the US government is also under pressure from the business circle, as many US companies, keenly aware of competition from China, are concerned about losing their core technologies and unduly assume China is stealing from them.