China denied allegations of backing hackers to launch cyber attacks against other countries, stressing that it is in the common interests of the world to responsibly safeguard international cyber security.

It's unprofessional and irresponsible to accuse China before verifying the anonymous hackers' identification, Defense Ministry spokesman Yang Yujun told a news conference on Thursday.

Yang's remarks were made in response to a number of recent reports playing up "China's cyber warfare".

According to a report by US Northrop Grumman for the US-China Economic and Security Review Commission, Beijing is funding research to bolster cyber attacks against US military commands and the contractors that serve them, particularly telecommunications systems.

The report issued earlier this month warned that Chinese telecommunications firms also maintained relationships with the People's Liberation Army, while these companies were giving the PLA access to cutting-edge research and technology.

"Cyber sabotage is illegal and forbidden in China, and would be severely punished," Yang said.

"China itself is also the victim of cyber attacks," he said.

In 2011, about 47,000 overseas IP addresses controlled nearly 8.9 million computers in China. From January to March this year, the websites of China's Defense Ministry and China Military Online suffered 240,000 cyber attacks, according to the Defense Ministry.

Cyber security is a common challenge faced by all countries, said Yang, urging related parties to share the responsibility of strengthening cyber security, instead of destroying mutual trust through arbitrary accusations and charges.

Wen Weiping, a professor with School of Software and Microelectronics of Peking University, said that it is difficult to trace the countless attackers' identities, let alone determine who their supporters are.

"Actually China is quite vulnerable to cyber attacks because of the limited cyber technology or security awareness," he said.

In response to questions about the size of its 2012 defense budget, Yang said China's military spending depends on its defense needs and development strategies.

China increased its defense budget by 11.2 percent to 670 billion yuan ($106 billion) in 2012 during the National People's Congress earlier this month.

The growth in military spending has aroused the attention of foreign countries.

The increase is mainly to fund efforts to raise the standard of living of service people amid inflation, upgrade outdated armaments and infrastructures, as well as to meet the soaring need to safeguard expanding overseas interests, Yang said.

While China's military spending amounted to 1.28 percent of its GDP in 2011, spending by the world's major military powers exceeded 2 percent, the spokesman said.

"China's defense budget is only one-sixth of that of the US this year," he said.

Yang added that China is transparent with its defense figures, refuting charges that the actual figure was underreported.

It's difficult for China to hide extra expenses since all of its military expenditures come from the state, which publishes the budget during the annual NPC meeting, said Pan Zheng, a researcher at the National Defense University.