By James Pomfret

HONG KONG (Reuters) - Chinese authorities have carried out a rare crackdown on the sex trade in the "sin city" of Dongguan following a candid report by the state broadcaster on the underground industry.

China outlawed prostitution after the Communist revolution in 1949, but it returned with a vengeance following landmark economic reforms three decades ago, and has helped fuel a rise in HIV/AIDS and sexually transmitted diseases.

While the government carries out periodic crackdowns, it is unusual for state media to cover them in such a high-profile way or for top officials to comment on the problem, underscoring worry about the explosion of the sex trade.

Media said 67 people were arrested and 12 venues were shut down in a sting operation involving thousands of police in the Dongguan region at the heart of China's Pearl River Delta industrial hub in the southern province of Guangdong.

Provincial Communist party boss Hu Chunhua, stressed the need "to conduct an extensive trawling-style crackdown on the entire city", according to a report in the Nanfang Daily.

Two city police chiefs had been suspended, Hong Kong's South China Morning Post reported.

China's main state broadcaster, China Central Television (CCTV), aired a half-hour report on Sunday chronicling what appeared to be extensive and open prostitution in five towns across Dongguan.

Secretly shot footage showed scantily clad women parading on a stage and managers of venues speaking openly about prostitution services.

The CCTV report was widely watched across China and followed with interest and widely commented on on social media.

While periodic sweeps against vice have been carried out, including during sensitive periods such as the 2008 Beijing Olympics and 2010 Asian Games in Guangzhou, the industry has thrived. Law enforcement often appears to be lax.

The Dongguan region has long been known as a hub for the sex industry.

Authorities there said last month the city had seen a high incidence of HIV/AIDS amid rumours that more than 2,700 sex workers had been infected, according to the Global Times, a Chinese tabloid owned by the Chinese Communist Party mouthpiece, the People's Daily.

(Additional reporting by Paul Carsten in Beijing; Editing by Ben Blanchard and Robert Birsel)