A top Chinese government official has urged authorities to be "more forceful" in the way they manage the web, state media said, as Beijing tries to tighten online controls over fears of social unrest.

Wang Chen, head of the State Internet Information Office -- a government body set up this year to supervise online content -- also urged officials to use the web to "guide public opinion and promote positive social values".

"All regions and departments must... use more forceful and effective measures to strengthen the construction and management of cyber culture," he was quoted as saying by the official Xinhua news agency late Saturday.

With more than half a billion Chinese now online, authorities in Beijing are concerned about the power of the Internet to influence public opinion in a country that maintains tight controls on its traditional media outlets.

And as the nation's economy loses steam amid financial woes in Europe and the United States, China's leaders are increasingly fearful of social unrest.

Large-scale strikes have hit China in recent weeks, as workers resentful about low salaries or layoffs face off with employers juggling high costs and slowing exports -- news that quickly spreads round the country via the web.

Leading Internet firms have already been pressured to tighten their grip on the web, with propaganda chief Li Changchun, fifth in the Communist Party hierarchy, meeting the heads of China's main search engine Baidu in September.

That same month, the head of Sina said the web giant -- owner of China's most popular Twitter-like microblogging service, or weibo, which has more than 200 million users -- had set up "rumour-curbing teams", apparently in response to government pressure.

But still the Internet has posed a huge challenge to government attempts to block content it deems politically sensitive through a censorship system known as the "Great Firewall".

The number of weibo users has more than trebled since the end of 2010, according to government data, and the speed with which they have taken off has made it impossible for censors to keep up.