China supports international efforts to secure cyberspace but believes each nation's "Internet sovereignty" must be respected, a top Chinese official said at a cyber security conference on Tuesday.

"China, like many other countries, is very concerned about cyber security," said Liu Zhengrong, deputy director general of the Internet Affairs Bureau of the State Council Information Office.

"China faces severe cyber security threats," Liu told participants here at the Worldwide Cyber Security Summit, a gathering of government and business leaders from 40 countries hosted by the EastWest Institute think tank.

"International cooperation is much needed to safeguard international cyberspace," Liu said.

But "Internet sovereignty of each country needs to be respected," the Chinese official added. "Different national and cultural conditions" should be taken into account.

Liu declined to answer repeated questions about cyber attacks last year on Google which the Internet giant said originated in China and led to the California company's decision to reroute its searches through Hong Kong.

"The Chinese government firmly opposes cyber attacks in any form and Chinese law clearly states that any hackers will be held liable for their actions," he said.

Liu said China itself is a "a major victim of cyber attacks and network viruses" and has laws in place to deal with hackers.

"Internet-related crimes (in China) are showing a steady upward trend," Liu said. "We suffer big economic losses from hacking networks and viruses - around $1 billion dollars (6.8 billion yuan) a year."

In 2009, Chinese law enforcement authorities investigated about 48,000 cases, a 37 percent increase over 2008, he said.

While China has a dynamic Internet population of more than 400 million users and millions of bloggers, there is no "absolute freedom" on the Web, Liu said.

"I don't think there is absolute freedom in this world," he said. "When you are speaking via the Internet you must abide by laws and respect others' lawful rights."

Last Thursday, Wang Chen, minister of the State Council Information Office, said China has been actively promoting a real-name registration system for Internet and cell phone users to better manage Internet information and services.

China needs laws that will step up monitoring for "harmful information" and block "overseas hostile forces from infiltrating through the Internet," Wang said.

Last week, China tightened its State Secrets law, holding Internet and mobile phone operators responsible for customers who try to leak State secrets.

Some 400 government officials, business leaders and cyber security experts are attending the summit, which features three days of discussions on ways to protect the world's digital infrastructure from electronic threats.