The jaw-dropping Hong Kong protests have kicked up another gear after one of the city's best known activists walked free from prison and waded into the unprecedented unrest.

Joshua Wong, one of the leaders of 2014's pro-democracy protests, left jail and demanded the resignation of the city's leader.

"I will join to fight against this evil law," said the 22-year-old, who has been behind bars for five weeks for contempt of court. "I believe this is the time for her, Carrie Lam the liar, to step down."

Citizens flooded the streets over the weekend to protest against Beijing-backed Ms Lam's plan to bring in a new law to allow extradition of suspects to mainland China to face trial.

Organisers said as many as two million of a population of seven million protested, although police said just 338,000 took part in the rally.

Riot police fought protesters with tear gas and batons in clashes that have grown increasingly violent since the demonstrations began on June 9. Activists set up barricades, wore masks and poured water on gas canisters in mass protests the like of which have not been seen in the city.

The sea of people waved umbrellas in an echo of the 79-day 2014 movement when they were used to defend activists from pepper spray and tear gas.

'THE DAMAGE HAS BEEN DONE'

City chief executive Ms Lam has agreed to suspend the law to end the unrest, but activists fear it could be reintroduced later, and want the proposal completely dropped.

They attacked her apology, issued on Sunday without any concessions to protesters' demands she revoke the bill, stand down and agree to not prosecute individuals.

Mr Wong told German news outlet Deutsche Welle that Ms Lam's apology was "useless because the damage has been done".

On Monday, protesters dressed in black moved from occupying a stretch of highway to surrounding the entrance to the chief executive's office, as the executive council held an extraordinary meeting to discuss the bill and Ms Lam's future.

The council declared its support for the former civil servant, who vowed to unite the city when she took the leadership in 2017. Instead, she is at the centre of one of the worst crises Hong Kong has faced in more than a decade.

Last Wednesday, she played on her image as the city's nurturing "Nanny" as she cried on national TV. "If I indulge his wayward behaviour, he might regret it when he grows up," she said of Hong Kong.

The former British colony was handed back to China in 1997 with a guarantee of autonomy, and that the territory would have its own legal and political system.

But concerns have been growing that the mainland government has been steadily pushing the boundaries ever since - with an inherent contradiction at the centre of the "one country, two systems" framework.

The latest conflict can be seen as a flashpoint in the tensions between China's communist government and the liberal ideals of West.

These are the territory's biggest protests since 2003, when residents took to the streets to rally against plans for tighter national security laws. The protests were successful - the proposal was dropped and the leader resigned.

But the tensions persisted, and disorder returned in 2012 and 2014, when pro-democracy campaigners called for changes to how the city's chief executive was chosen.

As chief secretary for the administration, Ms Lam led the task force, but instead of real reform, it was decided that a limited number of candidates approved by a small "nomination committee" would be allowed to run. The decision sparked the Umbrella Movement, calling for true democracy in the region, but it did not achieve its aims.

Now, the cycle has come around again, with renewed fury, as the international community watches the renewed chaos with bated breath.

"I hope governments around the world will support activists in Hong Kong who face prosecution and are physically assaulted by police," Mr Wong said.

'FIGHTING FOR THEIR FREEDOMS'

On Monday, China's Foreign Ministry expressed "strong dissatisfaction" over foreign media coverage of the protests. "Individual Western media ignored the facts, recklessly commented on Hong Kong's legislative revision, and publicly provoked external forces to interfere in Hong Kong's affairs," the ministry said in a statement.

But it has held back from going further, insisting the idea for a law change came from Ms Lam. The city leader has been called a Beijing puppet - but how far it will support her could mean everything for her survival.

Chinese President Xi Jinping has cemented his hold on power since taking the helm in 2012, expanding government control of information, religion and media.

The Hong Kong government has disqualified a pro-independence party, sent the leaders of a 2014 protest to prison and denied a visa renewal to an editor for Britain's Financial Times.

Activists decried these moves as chipping away at Hong Kong's freedoms, but residents largely went about their lives - until now.

Mr Xi is trapped in a balancing act between attempts to tighten Communist authority and stability in the international financial centre, and wanting to keep Hong Kong from slipping out of Beijing's control - or even demanding independence.

China's leader has other problems, in the form of an escalating US trade war, and does not want Hong Kong to become leverage when he meets Donald Trump at the G20 summit in Japan next week.

"It is a sign that Xi Jinping's government is not totally impervious to pressure, despite the fact that he has consolidated so much power," said Ben Bland, an expert at the Lowy Institute and author of Generation HK: Seeking Identity in China's Shadow.

"The Chinese government is determined to stop what it sees as the use of Two Systems to undermine the unity of One Country. And Hong Kongers are clearly determined to fight for their freedoms."

- With wires