A Guangzhou-based anti-graft activist is in the middle of five days of detention in Changsha, Hunan Province after being detained by the police for allegedly soliciting prostitutes.

The Changsha public security bureau stated via its official Sina Weibo account that the 62-year-old Ou Shaokun and another man surnamed Xian, 47, were found by police in a hotel with two prostitutes in their 20s at around 11 pm on Thursday after they received an anonymous tip-off from a member of the public.

According to the statement, the women have confessed to selling sex and the men have confessed to soliciting prostitutes, and all four have been held in administrative detention.

The police declined to provide further details about the case when reached by the Global Times.

Ou, an unemployed resident of Guangzhou, Guangdong Province that lives on government benefits, is well-known for campaigning against the use of official vehicles for personal purposes since 2005.

He is known as Uncle Ou and has more than 100,000 followers on Sina Weibo.

The latest post on Ou's Weibo on Thursday afternoon said that he had informed the Guangzhou disciplinary watchdog about two Guangdong government vehicles that were being used for private purposes in Hunan.

"It might be a frame-up due to the bold disclosures he made regarding the private use of official cars," Li Haixia, a lawyer close to Ou, told the Global Times, claiming that Ou has been unfairly treated. 

Ou has previously claimed that his and his mother's benefit payments have been reduced due to his campaign, media reported.

Li added that he has been unable to reach Ou.

However, some netizens also pointed out that being a model anti-graft campaigner does not mean that Ou is not able to make mistakes. It should not affect the credibility of his previous efforts if Ou is indeed a lawbreaker.

"In all, everyone - including both Ou and the government  - is being watched to prevent violations," wrote a commentator on news portal gmw.cn.

A person found to have solicited prostitutes is usually detained for 10 days, so his five days of detention may indicate that he has confessed to attempting to solicit prostitutes, according to Li.

Guangzhou's Intermediate court will hear a case brought by Ou against the Guangzhou supervisory bureau on Monday, according to a notice on its website. Ou has previously demanded the bureau disclose its regulations about the use of government vehicles.

Ou estimated that he got feedback on about 80 percent of hundreds of complaints he filed to the local disciplinary authorities, but only 10 percent of the cases have been identified as the illicit personal use of official cars. The harshest punishment that an official can receive for this offence is to be criticized by their superiors and have their bonuses suspended for three months, the Beijing Youth Daily reported in 2013.