China on Wednesday refuted allegations of hacking activities as groundless, calling for international cooperation to fight cyber crime rather than criticize each other in an irresponsible way.

Foreign Ministry spokesman Hong Lei made the remarks at a regular press briefing, noting that groundless criticism is "irresponsible and unprofessional, which will not help to solve the problem."

US cyber security firm 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.

"Firmly opposing cyber attacks, China has established relevant laws and regulations to crack down on hacking," Hong said.

China has been a major victim of cyber attacks, most of which are from the United States, according to Hong.

He said China and the United States have maintained communication over the issue, adding that as cyber crime is an international problem, it should be solved through international cooperation on the basis of mutual trust and respect.

Earlier on Wednesday, China's military spokesman also said 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.

It 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, Geng Yansheng, spokesman for the Ministry of National Defense, said at a briefing.

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

Secondly, 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.

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

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.

He added, "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 hacking, the Chinese side would like to resolve the issues through joint law enforcement and consultations with other countries.

According to Geng, 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. Also, China has established bilateral law enforcement cooperation with more than 30 countries 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 said.

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

It signaled that the United States is looking for fresh topics over which to criticize China in an 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 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 business, 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.