A Chinese man apologised on state television Tuesday after being detained for "publishing false stories" on an overseas news portal alleging gross rights abuses, the latest step in a wide-ranging crackdown on "Internet rumours".

Xiang Nanfu, 62, had posted untrue stories on the Chinese-language site Boxun since 2009 that "seriously harmed the image of the state" and "had a very bad impact", a statement on the Beijing police website said.

Hundreds of Chinese bloggers and journalists have been arrested in recent months as part of a government-backed campaign to assert greater control over social media, which has seen influential critics of Beijing paraded on state television.

The clampdown, which began last year, appears to be part of a concerted effort by China's ruling Communist party, which maintains an iron grip on power, to rein in criticism.

"My behaviour has had a very bad impact. I recognise I have smeared the (Communist) Party and the government. My behaviour is criminal behaviour," said Xiang, in a nine-minute news report on China Central Television (CCTV).

"How can I apologise to the party and the government, let alone apologise to my family?

"I am truly, extremely regretful. I hope the government can give me the opportunity to mend my ways, make contributions and become a new person."

Among the rumours Xiang was alleged to have created was that the Chinese government "removed" organs from living people and "buried people alive", the police statement said.

Another claim was that more than 1,000 policemen violently expropriated land, including beating a pregnant woman to death, it added.

The television report showed covert images of Xiang surfing the web in Internet cafes, and him being led away from his apartment after it was raided by police accompanied by a television crew.

Boxun, which often reports unsourced rumours, issued a statement on its website describing Xiang as a "Boxun journalist".

The statement denied the US-based website had reported on such organ removals or burying people alive, and linked the detention to China's recent Internet crackdown.

"We noted that a lot of Chinese web users and dissidents were detained by authorities recently. This is a clear sign that human rights in China are quickly deteriorating," the statement said.

At the start of the campaign last year, officials told Internet celebrities with millions of followers to "promote virtues" and "uphold law" online.

Soon after, Chinese-American billionaire blogger Charles Xue -- who regularly posted reform-minded comments on a variety of sensitive issues -- was arrested for suspected involvement in prostitution.

Links between the crackdown and the arrest of the popular blogger -- who had attracted 12 million online followers -- were routinely dismissed by state media.

Xue was paraded on state television, which also broadcast an interview with Pan Shiyi, another of China's most popular bloggers, in which he appeared contrite and warned of the dangers of "casual" online posts.

Qin Zhihui, the first person to stand trial in the Internet crackdown, was jailed for three years last month after he confessed his guilt and made a lengthy statement of remorse, even thanking his detention centre.

Under regulations announced last September, Chinese Internet users face three years in prison for writing defamatory messages that are re-posted 500 times. Web users can also be jailed if offending posts are viewed more than 5,000 times.