Hong Kong, Jun 17 (AFP) Leading Hong Kong democracy activist Joshua Wong walked free from prison on Monday and vowed to join historic anti-government protests rocking the city, calling on the city's embattled pro-Beijing leader to quit.

Organisers said some two million people marched in tropical heat on Sunday calling for the resignation of chief executive Carrie Lam, rebuking a now abandoned bill that would have allowed extraditions to the Chinese mainland.

The city has witnessed unprecedented scenes as public anger boils towards the city's leaders and Beijing, with two record-breaking rallies a week apart punctuated by violent clashes between protesters and police armed with tear gas and rubber bullets.

Wong, the poster child of the huge pro-democracy "Umbrella Movement" protests in 2014, became the latest voice to call for Lam's resignation as he was released from a sentence imposed over his leadership of those demonstrations.

"She is no longer qualified to be Hong Kong's leader," he told reporters. "She must take the blame and resign, be held accountable and step down." "After leaving jail today I will also fight with all Hong Kongers to oppose the evil China extradition law," he added.

Wong was sent to prison in May and was eligible for early release for good behaviour -- there is no indication the move was linked to the current protests.

Opposition to the extradition bill united an unusually wide cross-section of Hong Kong in recent weeks, from influential legal and business bodies to religious leaders.

And while the spark for the last week of protests has been the threat of extradition to China, the movement has since morphed into the latest expression of public rage against both the city's leaders and Beijing.

Many Hong Kongers believe China's leaders are stamping down on the financial hub's unique freedoms and culture.

They point to the failure of the "Umbrella Movement" to win any concessions, the imprisonment of protest leaders, the disqualification of popular lawmakers and the disappearance of Beijing-critical booksellers, among recent examples.

Critics feared the Beijing-backed extradition law would entangle people in China's notoriously opaque and politicised courts and damage the city's reputation as a safe business hub, sparking unprecedented turnouts.

Throngs of largely black-clad protesters snaked their way for miles through the streets to the city's parliament throughout Sunday -- with the organisers' estimate for the crowd size doubling an already record-breaking demonstration the previous Sunday in the city of 7.3 million.

The estimate has not been independently verified but if confirmed it would be the largest demonstration in Hong Kong's history.

Police, who historically give far lower estimates for political protests, said 338,000 people turned out at the demonstration's "peak" Sunday.

By Monday morning the massive crowds had dramatically dropped to just a few hundred largely young protesters who blocked a major highway outside the city's parliament and some nearby streets.

But they later ended their occupation peacefully, most of them moving to a nearby park.

The extradition furore is just the latest chapter in what many see as a battle for the soul of Hong Kong.

Many Hong Kongers believe China's leaders are stamping down on the financial hub's unique freedoms and culture.

In recent years, the city's pro-Beijing leaders have successfully resisted bowing to pressure from large street protests led by the city's pro-democracy activists.

But the sheer size of the last week's crowds, and unprecedented violent clashes on Wednesday, forced Lam into a major climbdown.

On Saturday she indefinitely suspended the unpopular extradition bill and apologised a day later for the attempt causing "conflict and disputes".

But the U-turn has done little to mollify protesters.

The Civil Human Rights Front, which is organising the rallies, has called on Lam to resign, shelve the bill permanently and apologise for police using tear gas and rubber bullets on Wednesday. They have also demanded all charges be dropped against anyone arrested.

The violent crowd control measures on Wednesday, used by police as protesters tried to storm the city's parliament to stop the bill being debated, have proved enormously costly for Lam's government.

Political allies -- and even Beijing -- distanced themselves from her as public anger mounted.

"I think she has lost any remaining credibility or legitimacy to rule in Hong Kong because of her own mishandling of this whole affair," lawmaker Charles Mok told RTHK Radio.

The massive rallies -- which come 30 years after the Tiananmen crackdown -- also create a huge headache for president Xi Jinping, the most authoritarian Chinese leader since Mao Zedong.

Under the 1997 handover deal signed with Britain, China agreed to allow Hong Kong to keep unique liberties such as freedom of speech and its hugely successful independent common law courts for 50 years.

But the huge crowds this week illustrate how many Hong Kong's 7.3 million inhabitants believe China is already reneging on that deal and fear further sliding freedoms as the city hurtles towards that 2047 deadline.

Chinese state media remained largely silent about Sunday's historic rally, with social platforms scrubbed clean of any pictures or mentions of the rally. (AFP)

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