Thousands of demonstrators have marched through Hong Kong in defiance of a police ban, as shops closed amid fears of renewed violence.

A mixed crowd of hardcore protesters in black and wearing masks, along with families with children, spilled into the roads of the Causeway Bay shopping belt and marched for more than a mile to the Central business district.

Some waved US and British flags, while others carried posters reiterating their calls for democratic reforms.

Hong Kong Protests
Protesters hold placards and British flags during a peaceful demonstration outside the British Consulate in Hong Kong (Vincent Yu/AP)

Police had turned down a request by the Civil Human Rights Front to hold the march, but the demonstrators were undeterred, as they have been all summer.

“I feel this is our duty. The government wants to block us with the ban, but I want to say that the people will not be afraid,” said one protester, Winnie Leung, 50.

The march disrupted traffic and many shops, including the Sogo department store, closed their doors.

Protesters burned Chinese flags and tore down banners congratulating China’s ruling Communist Party, which will celebrate its 70th year in power on October 1.

In familiar scenes, some protesters smashed glass windows and surveillance cameras at a subway station exit.

Hundreds of protesters later targeted the government office complex, throwing bricks and petrol bombs through police barriers.

Police responded by firing volleys of tear gas and using water cannon ;orries to spray chemical-laced water as well as blue liquid that helped them identify offenders, in a repeat of confrontational scenes from the last several weeks of the protests.

Protesters retreated but regrouped in the nearby Wan Chai neighbourhood, setting fires outside a subway station exit and on the streets.

They fled again after riot police advanced and the cat-and-mouse battles went on for a few hours before calm returned.

Police fired tear gas again later in the nearby North Point area after protesters obstructed traffic after brawling there earlier with pro-government supporters.

Hospital authorities said eight people were injured throughout the day, including three in serious condition.

Hong Kong Protests
Protesters carry US flags and a placard reading You trust Communist party? as they march on a street in Hong Kong (Vincent Yu/AP)

The protests were triggered in June by an extradition bill that many saw as an example of China’s increasing intrusion and at chipping away at Hong Kong residents’ freedoms and rights, many of which are not accorded to people in mainland China.

Hong Kong’s government promised this month to withdraw the bill, which would have allowed some criminal suspects to be sent to mainland China for trial, but protesters have widened their demands to include direct elections for the city’s leaders and police accountability.

There have been increasing clashes between protesters and police, who demonstrators have accused of abuses.

More than 1,300 people have been arrested since the protests started.

The unrest has battered Hong Kong’s economy, which was already reeling from the US-China trade war. It is also seen as an embarrassment to China’s ruling Communist Party ahead of October 1 National Day celebrations.

Earlier on Sunday, hundreds of protesters waved British flags, sang God Save The Queen and chanted “UK save Hong Kong” outside the British Consulate as they stepped up calls for international support for their campaign.

With banners declaring “one country, two systems is dead,” they repeated calls for Hong Kong’s former colonial ruler to ensure the city’s autonomy is upheld under agreements made when it ceded power to China in 1997.

Demonstrators held similar rallies on September 1 at the British facility and last weekend at the US Consulate.