A controversial Chinese professor has sparked an outcry by calling Hong Kong people "bastards", "dogs" and "cheats" after a spat between mainlanders and locals in the southern city went viral online.

Kong Qingdong -- famous for his public use of profanities -- made the comments after the video showed a mainland girl being rebuked by locals angry that she was flouting rules against eating aboard Hong Kong subway trains.

The incident has been described as an example of the culture clash between mainland China and Hong Kong, with many pointing to what they see as a prevalent sense of superiority among residents in the former British colony.

"Everybody should have a duty to speak Mandarin," Kong, a professor of Chinese studies at the prestigious Peking University who says he is a descendent of the philosopher Confucius, said in an interview posted on online video website v1.cn last week.

"What type of people are those who deliberately don't speak Mandarin? Bastards!" he said, referring to the Hong Kong people involved in the row, who spoke in their native Cantonese language.

"As far as I know, many Hong Kong people don't regard themselves as Chinese. Those kinds of people are used to being the dogs of British colonialists -- they are dogs, not humans."

Kong also says the British dealt with "Hong Kong dogs by spanking them" before they handed the territory back to China in 1997, and accuses many Hong Kong people of swindling and cheating.

Furious netizens in Hong Kong have vented their anger, with many attacking mainland China in sometimes vicious comments.

"I see a fat dog barking, all I can say is, please take a look at your own country before u comment on other people," one online user wrote, before listing perceptions about what is wrong with mainland China.

The video of the subway train incident can be seen at www.youtube.com/watch?v=wEComrx76uY and the professor's response is at www.youtube.com/watch?v=_nUkiaDS3g4.

Around 150 people protested at Kong's comments on Sunday evening outside Beijing's liaison office in Hong Kong, police in the territory said.

Hong Kong trade union lawmaker Lee Cheuk-yan said the outcry was evidence of growing tensions between people in the territory and on the mainland.

"This is a ticking time bomb," he said.

"Hong Kong people are unhappy with the central government, we are disgruntled about the lack of democracy. On a more day-to-day level, you see that Hong Kong people often have clashes with mainlanders."

While mainlanders have long complained about the perceived arrogance of wealthy Hong Kongers, Lee pointed to two recent episodes that have fostered a sense of resentment among locals in the city.

Last week, Italian clothing chain Dolce & Gabbana apologised to the people of Hong Kong for allegedly discriminating against them in favour of newly wealthy mainland shoppers.

And with the auspicious Year of the Dragon starting on Monday, mothers-to-be in Hong Kong complain they have been shut out of maternity wards because so many pregnant mainland women have come to the city to give birth.

Kong himself has reportedly backtracked from the controversy, claiming in a subsequent interview that he did not mean all Hong Kong people were "dogs" but said some people who kowtowed to colonialism were dogs.

The professor is no stranger to controversy. He was reportedly involved in a shadowy "Confucius Peace Prize" that awarded its annual award to Russian Prime Minister Vladimir Putin last year.

The furore has highlighted the wide gap that still exists between mainland China and Hong Kong, which since the handover from British rule has been run as a "special administrative region" with its own legal and economic systems.

A survey published last month by the University of Hong Kong revealed that only 17 percent of people in the territory identified themselves as Chinese, the lowest percentage since 2000, Beijing's China Daily newspaper said.