A well-known state television presenter's call for China to kick out "foreign trash" and two highly publicised incidents of bad behaviour by visitors have set off a heated debate on foreigners in China.

The vitriolic comments posted online by Yang Rui, who presents a daily talk show in English on the state-run China Central Television network, have channelled into a growing controversy playing out on China's popular microblogs.

"The Public Security Bureau needs to clean out the foreign trash," wrote Yang on his microblog, accusing expatriates of "engaging in human trafficking" and "spreading lies" about China.

He made his comments after Beijing police last week launched a 100-day crackdown on foreigners working illegally in the capital, with posters showing a clenched fist and a phone line for residents to inform on visa violators.

Yang urged police to focus on areas popular with expatriates in Beijing, and also welcomed the recent expulsion of Al Jazeera journalist Melissa Chan, which has been strongly condemned by rights organisations and by Washington.

"We kicked out that foreign harpy and closed Al Jazeera's Beijing bureau. We should shut up those who denigrate China and send them packing," wrote Yang, whose comments have been widely criticised in the foreign media -- though his employer, CCTV, has remained silent.

In a statement Tuesday, Yang said he intended his comments to be a "wake-up call" for foreigners who violated China's laws, citing the recent example of a British tourist accused of sexually assaulting a Chinese woman.

The man, who is now believed to be in custody, was caught on camera and the footage went viral after it was posted online, sparking a barrage of anti-foreigner sentiment.

Just days later, footage showing a Russian cellist verbally abusing a female passenger on a train in China was posted online, adding further to the growing controversy.

The cellist has since been fired from his position with the Beijing Symphony Orchestra, which said its reputation had been "badly damaged" by the actions of Oleg Vedernikov, a move welcomed by many Chinese bloggers.

Vedernikov has apologised over the May 14 incident, but this has done little to dampen the controversy over his actions.

By Tuesday the behaviour of foreigners remained a much discussed topic on microblogs in China, where national resentment over historic humiliations at the hands of foreign powers persists.

"We are too indulgent towards foreigners and that is why they are so badly behaved," posted one web user.