The demonstration in the town of Sheung Shui, not far from the Chinese city of Shenzhen, started peacefully but devolved into scuffles and shouting, with police firing pepper spray at protesters who threw umbrellas and hard hats.

The protest is the latest in a string of demonstrations that has roiled the former British colony for more than a month.

Sometimes street protests have drawn in millions, with hundreds storming the legislature on July 1 to oppose the extradition bill that would have allowed criminal suspects in Hong Kong to be sent to China to face trial.

Critics see the bill as a threat to Hong Kong's rule of law.

Chief Executive Carrie Lam this week said the bill was "dead" after having suspended it last month, but opponents are demanding a formal withdrawal.

Protests against the bill had largely taken place in the central business district, but demonstrators have recently begun to look elsewhere to widen support by taking up narrower, more domestic issues.

In Sheung Shui as protesters chanted demands in Mandarin, China's official language, for Chinese traders to go home.

Mainland traders have long been a source of anger among those in Hong Kong who say they have fuelled inflation, driven up property prices and dodged taxes.

Similar protests have included a march last week by nearly 2,000 people in the Tuen Mun residential district to protest against what they saw as the nuisance of brash singing and dancing to Mandarin pop songs.

On Sunday, tens of thousands marched in one of Kowloon's most popular tourist shopping areas, trying to persuade mainland Chinese tourists to back opposition to the extradition bill.

When former colonial ruler Britain returned Hong Kong to China in 1997, Chinese leaders promised the city a high degree of autonomy for 50 years.

But many say China has progressively tightened its grip, putting Hong Kong's freedoms under threat through a range of measures such as the extradition bill.

Australian Associated Press