A prominent online whistle-blower said yesterday police had questioned him over suspicions of swindling and blackmail and detained him for 24 hours.
The news came as the government is stepping up its crackdown on citizens' internet activities.
Wu Dong, better known by his online name of Huazong, or “Boss Hua”, was picked up at a hotel in Beijing on Tuesday and taken in for questioning.
“They say I’m suspected of swindling and blackmail,” he said by telephone. “Of course this is not true and I’m innocent. I think somebody has it in for me.”
Wu declined to say if he thought he was targeted because of his activity online, which he said the police did not bring up.
“I really can’t speculate on that,” he said.
Reuters was unable to reach Beijing police for comment.
Wu, who specialises in identifying the luxurious watches worn by Chinese officials in online pictures, became famous last year for his leading role in bringing down a corrupt official who first aroused public ire after he was pictured smiling at the scene of a bus accident in which 36 people died.
Criticism grew when pictures of the official wearing high-end watches - as identified by Wu - that he could not possibly afford on his salary were then posted on social media sites.
The official, Yang Dacai, was sacked and then jailed this month for 14 years after being found guilty of corruption.
Wu said he was now in a state of legal limbo.
“They may decide to press charges against me, but they may also stop the investigation,” he added.
Chinese President Xi Jinping has made fighting graft a top theme of his new administration, and has specifically targeted extravagance and waste, seeking to assuage anger over corruption and restore faith in the party.
While the party has encouraged people to use the Internet to expose graft, especially for lower-level officials like Yang, it has detained activists who have called for officials to publicly disclose their assets.
Wary of any threat to its authority or social stability, the party has also stepped up its already tight controls over social media to limit public discussion of sensitive political issues.
Last week the government unveiled tough measures to stop the spread of what it called irresponsible rumours, threatening three years in jail if untrue posts online were widely reposted.