Hong Kong police fired rounds of tear gas on Saturday outside the local headquarters of the China People's Liberation Army to try to disperse anti-government protesters.

Hong Kong democracy activist Joshua Wong arrested

Hong Kong protesters expected to regroup despite police ban

Hong Kong protesters broke down protection barriers outside the city's government headquarters and threw petrol bombs at police, as tens of thousands took to the streets in defiance of a ban.

Protesters react after police fired tear near the government headquarters of Hong Kong. Anthony Wallace/AFP

A hardcore group of violent protesters armed with shields and throwing rocks were sprayed with water cannon.

The group smashed down a barrier erected around the government's parliament building.

Police fired water cannon and tear gas at Hong Kong pro-democracy protesters massed outside the city's parliament on Saturday, as demonstrators defied a ban on rallying, the arrests of leading activists and rising threats from China, to take to the streets for a 13th straight weekend.

Police had banned the demonstration on security grounds, then organisers had cancelled it, after last weekend saw some of the most violent clashes in months of political turmoil.

But large crowds, many in their signature black T-shirts and under a colourful canopy of umbrellas, snaked through Hong Kong island anyway, blocking roads in the financial heart and chanting "reclaim Hong Kong, revolution of our times."

Tensions rose as the afternoon wore on, with hardcore protesters throwing rocks, setting fires — and shining laser pens — at a rank of police behind a barricade at the city parliament known as the Legislative Council (LegCo).

Police fired a water cannon and rounds of tears gas to disperse the group, as protesters dug up the pavement to use as projectiles and crouched under umbrellas.

Demonstrators react after police fired tear gas during a protest in Hong Kong, China, on Saturday. Reuters

As dusk drew in, protesters smashed through the barrier outside the parliament building.

The LegCo was stormed on July 1 — the 22nd anniversary of the handover of Hong Kong from British to Chinese rule.

Earlier protesters marched by the official residence of Hong Kong's embattled Beijing-backed leader Carrie Lam, who is the focal point of anger after trying to pass a bill which would have allowed extradition to China.

"I'm prepared for the consequences of coming out," said one protestor, who gave his name as Jay, adding "Hong Kongers have the right to assembly."

Protesters march with a banner that uses the stars of the Chinese flag to depict a Nazi Swastika symbol. AFP

Opposition to the extradition bill — now suspended but not permanently withdrawn — has brought much of Hong Kong to the streets.

The protests have expanded into a wider pro-democracy call and a rejection of attempts by Beijing to curtail the freedoms of the semi-autonomous territory.

Another big group massed in the busy shopping district of Causeway Bay, occupying the road and chanting anti-government slogans.

"I'm not afraid to come out here today," said another 25-year-old protester who gave his surname as Ng.

A man refers to the demands of the anti-government protests, at a march in Hong Kong. Anushree Fadnavis/Reuters

A helicopter buzzed above marchers as police appealed to the public to "leave immediately" while water-cannon trucks were driven onto the streets.

But protesters were in defiant mood.

"It's 'now or never' for Hong Kong, " said a 33-year-old accountant who gave her surname as Wong.

"I'm a mother-of-two. They didn't come today but their grandmother did. We're defending the right of assembly for the next generation in Hong Kong."

Saturday marks the fifth anniversary of Beijing's rejection of a call for universal suffrage for Hong Kong, which sparked the 79-day "Umbrella Movement" in 2014.

Many protesters are determined not to let the new movement fizzle out as the Umbrella protests did.

At least five high-profile activists and three lawmakers were arrested on Friday in a sweep aimed at defanging Saturday's rally.

Rights groups say the tactics are cribbed directly from Beijing's protest playbook.

Two of the Umbrella Movement's leaders, Joshua Wong and Agnes Chow were among those arrested, charged and bailed for "inciting others to take part in unauthorised assembly".

The European Union's diplomatic chief Federica Mogherini said the developments were "extremely worrying", while US President Donald Trump said his economic pressure on China was forcing Beijing to take a more moderate line in Hong Kong.

Protesters sidestep ban

In an attempt to sidestep Saturday's protest ban, crowds earlier carried Christian crosses and sang "Hallelujah" in religious gatherings -- which do not require the same stringent permission from authorities.

Pro-democracy protestors march in central Hong Kong, on Saturday.

The demonstrators, who have earned a reputation for their creativity and unpredictability, also called for "mass shopping trips" in the city centre.

On Saturday morning, LIHKG, the Reddit-like forum used by protesters to communicate, reported via Twitter that its app had suffered the "largest attack it has ever seen".

Police on Friday confirmed three lawmakers -- and a district councillor -- had been arrested over their alleged actions in previous protests, but denied the sweep was timed specifically to weaken the weekend's protests.

More than 900 people have been arrested since June in connection to protests.

Hong Kong's crisis-hit government has refused to back down over the protests, which have seen millions march peacefully through the streets but also hardcore groups of radical protesters hurl bricks and petrol bombs at police armed with tear gas and rubber bullets.

The violence has damaged Hong Kong's reputation for stability and prosperity.

China has responded with a campaign of intimidation. State media on Friday reported that fresh military anti-riot drills were held across the border in Shenzhen.

Agencies