China should be cautious about "Internet mercenaries", a group of people posting comments online to manipulate public opinion, Zhao Qizheng, spokesman for the annual session of the National Committee of the Chinese People's Political Consultative Conference (CPPCC), said Wednesday in Beijing.

The influence of public opinion via the Internet is getting stronger as more and more people use the channel to exchange views and participate in political issues, Zhao said, noting that China had 457 million Internet users by the end of last year.

"We feel that Internet culture and environment is getting more complicated and there has emerged a group of people called 'Internet mercenaries'", he said.

Some of them, backed by institutions for certain purposes, disguise them as ordinary netizens and post comments in order to affect and divert public opinion, or even disturb government policy-making, he said.

It needs attention and alert from the government, and China lacks legislation in this regard, Zhao said.