A sea of democracy activists on Sunday once more flooded the streets of Hong Kong in a defiant show to the city's leaders that their movement still pulls wide public support, despite mounting violence and increasingly stark warnings from Beijing.

Ten weeks of demonstrations have plunged the financial hub into crisis, with images of masked black-clad protesters engulfed by tear gas during street battles against riot police stunning a city once renowned for its stability.

Communist-ruled mainland China has taken an increasingly hardline tone towards the protesters, decrying the "terrorist-like" actions of a violent hardcore minority among the demonstrators.

Despite the near-nightly clashes with police, the movement has won few concessions from Beijing or the city's unelected leadership.

The spiralling violence, which last week saw protesters paralyse the city's airport, has tarnished a campaign that had taken pride in its peaceful intent and unpredictability — which demonstrators have tagged with the slogan 'Be Water'.

Organisers of Sunday's rally, which started at the city's Victoria Park, said it was an attempt to wrestle the narrative of the protest back to its peaceful origins.

It is a "rational, non-violent" demonstration, according to organisers the Civil Human Rights Front, the driving force behind record-breaking rallies in June and July that saw hundreds of thousands of people hit the streets.

"We keep learning, the movement has evolved and become more fluid," the 25-year-old recent graduate, who gave his name only as Lo, told AFP.

Peace or violence?

China's propaganda apparatus has seized on the weeks of violence, with state media churning out a deluge of damning articles, pictures and videos.

State media also ran images of military personnel and armoured personnel carriers across the border in Shenzhen, prompting the United States to warn Beijing against sending in troops.

Analysts say any intervention by Chinese security forces would be a reputational and economic disaster for China.

But Hong Kong's police force are under intense pressure, stretched by flashmob protests and criticised for perceived heavy-handed policing including the use of tear gas, rubber bullets and beating demonstrators — incidents that have pinballed across social media.

"I think the way police have dealt with this is absolutely out of order. You can make your own judgement based on the many videos out there," protester James Leung told AFP.

Opinions among the protesters have diverged over the billowing violence, which has seen hardcore protesters using rocks, Molotov cocktails and slingshots against the police.

Some say the violence has driven the pro-democracy movement into an uncomfortable direction.

"There are some expressing extreme views," rally-goer Ray Cheng, 30, told AFP.

"But we have tried many times with peaceful approaches [...] I really hope the government can listen to us."

Many among Sunday's rally goers carried rucksacks stuffed with protest paraphernalia — laser pens, gas masks, googles and helmets.

"The consensus in online forums is that today is 'a peaceful, rational' gathering," said a 30-year-old identifying himself only as Man.

"We have our gear with us, but we hope not to use it."

A Hong Kong government spokesperson praised the police for handling "illegal acts with tolerance" and appealed to the protesters to "express their views in a peaceful and rational manner".

Unprecedented crisis

Hong Kong's unprecedented political crisis was sparked by opposition to a plan to allow extraditions to the Chinese mainland.

But protests have since morphed into a wider call for democratic rights in the semi-autonomous city.

Under a deal signed with Britain, authoritarian China agreed to allow Hong Kong to keep its unique freedoms when it was handed back in 1997.

But many Hong Kongers feel those freedoms are being chipped away, especially since China's hardline president Xi Jinping came to power.

Beyond suspending the extradition bill, Beijing and city leader Carrie Lam have shown no desire to meet key demands such as an inquiry into police violence, the complete withdrawal of the bill and an amnesty.

Beijing has turned the screws on Hong Kong's businesses, pressuring them to toe the line and condemn the protesters.

On Friday, Cathay Pacific announced the shock resignation of CEO Rupert Hogg after the carrier was excoriated by Beijing because some staff supported the pro-democracy protests.