Hong Kong protests are the latest in a wave of demonstration fuelling its biggest political crisis

Hong Kong protesters are set to rally for a second day on Sunday in an area popular with mainland Chinese shoppers as anger over the government's handling of an extradition bill revives other grievances, such as an influx of cross-border visitors.

On Saturday, a largely peaceful demonstration in a town close to the Chinese border turned violent as protesters hurled umbrellas and hardhats at police, who retaliated by swinging batons and firing pepper spray.

The protests are the latest in a wave of demonstrations that have rocked the former British colony for more than a month, fuelling its biggest political crisis since China re-gained control of the territory in 1997.

The focus of the rallies has switched from the extradition bill, which would allow people to be sent to mainland China for trial, to broader issues that have roused deep-seated tension between Hong Kong people and mainland Chinese.

Critics see the now-suspended bill as a threat to the rule of law in the Asian financial hub. Chief Executive Carrie Lam has said the bill is "dead", but opponents say they will settle for nothing short of its formal withdrawal.

Hong Kong returned to Chinese rule 22 years ago under a "one country, two systems" formula that allows freedoms not enjoyed in mainland China, including the freedom to protest and an independent judiciary.

Beijing denies interfering in Hong Kong affairs, but many residents are concerned about what they see as a relentless march toward mainland control.

Sunday's demonstration is targeted at mainland Chinese tourists in the town of Sha Tin, in the so-called New Territories between Hong Kong island and the border with China.

The town has previously been a battleground for Hong Kong people angry over the flood of Chinese day-trippers.

More than 23.6 million mainland Chinese visited Hong Kong in the first five months of this year, government data show, up 17.5% from a year earlier and the equivalent of at least three times Hong Kong's population of 7.4 million.

The government condemned violent acts during the protests on Saturday against so-called "parallel traders" from the mainland who buy bulk quantities of goods in Hong Kong which they then carry into China to sell for a profit.

In the past 18 months the government arrested 126 mainland visitors suspected of contravening their conditions of stay by being involved in parallel trading, it said.

It also refused entry to about 5,000 mainland Chinese suspected of being involved in parallel trading during that period, it added.