The campaign against the illegal sex trade in the booming southern entertainment city of Dongguan, Guangdong Province, will get tougher still, local police said on Tuesday.

Yan Xiaokang, director of Dongguan Municipal Public Security Bureau (PSB), promised that three months of intense activity would clean up KTVs, massage parlors and hotels involved in prostitution.

Almost 2,000 entertainment venues have been raided since the campaign began on Sunday night. By Tuesday, 39 establishments had been closed and 162 people were under investigation.

Lu Weiqi, deputy PSB director, said the police frequently raided known prostitution venues. In 2013, 981 sex trade cases were pursued in Dongguan and 350 people detained, Lu said.

Li Chunsheng, provincial vice governor and head of Guangdong PSB, said the campaign is not just about Dongguan but will cover the whole province. Teams will make unannounced visits to hotels and entertainment venues such as saunas, hotels, massage parlors and karaoke lounges.

Prostitution has been outlawed in China since the Communist Party of China (CPC) took power in 1949.

The problem is not just in China, but, according to a Tuesday comment piece in the CPC flagship newspaper the People's Daily, the international status of the sex trade makes the crackdown inevitable.

Ding Yu, sociology lecturer at Sun Yat-sen University, has studied the development of China's sex industry and the lives of those it employs. She echoed the view, saying that the raids have stuck a blow against the sex trade in accordance with the law.

The sex trade can result in a string of problems, including the spread of HIV, said Ding, one reason why many countries oppose prostitution. According to her, prostitution was traditionally considered a moral crime in China.

The harshness of the crackdown on illegal and immoral activities has triggered some sympathy for Dongguan's sex workers. Many aired their views online, claiming that sex workers are a vulnerable group whose privacy and rights should be respected. Some even attribute Dongguan's flourishing sex trade to migrant workers' sexual desire, inflamed by the process of urbanization.

Lu Weiqi describes a sex trade which involves a profit chain of hotel operators, contractors, managers, pimps and the sex workers themselves.

Limited police manpower has never succeeded in cleaning up the industry during past crackdowns, he said.

It is difficult for the police to collect evidence and identify the operators because of the so-called "protective umbrella" behind the scenes, according to Lu.

The information office of Dongguan has a hotline attached to its microblog for reporting illegal sexual services.

Anyone who provides protection to prostitution, including CPC cadres, government officials, and law enforcement officers will be severely punished, Li said.