Organisers say 1.7 million people turned out at Sunday's pro-democracy protest in Hong Kong, amid increasingly severe warnings by Beijing.
Police put the figure much lower at 128,000, counting only those at an officially sanctioned rally.
Activists and police have clashed over the past 11 weeks, but this weekend's protest remained peaceful.
The protests were sparked by a controversial extradition bill, which has since been suspended.
They have now morphed into a broader movement demanding democratic reform and an investigation into alleged police brutality.
The protest's organisers, the Civil Human Rights Front, were denied authorisation for a march through the city, but police allowed a pre-approved demonstration in the city's Victoria Park.
One of the marchers, named as Mr Wong, told the BBC's Lam Cho Wai at the scene: "We have been fighting for more than two months, but our government has no response at all. We could just come out again and again."
Large crowds also marched in the nearby areas of Admiralty, Causeway Bay and Wan Chai in defiance of the police ban.
A spokesman for the Hong Kong government said that although the demonstrations were generally peaceful, they had seriously affected traffic and caused much inconvenience.
He added that it was "most important to restore social order as soon as possible".
Reinvigorated faith in the cause
Stephen McDonell, BBC News, Hong Kong
The push to drive Hong Kong's pro-democracy movement in a more peaceful direction this weekend seems to have worked.
From toddlers to the elderly, protesters turned out to join a massive rally. Entire families were seen dressed in black getting soaked together when the heavens opened and driving rain struck the city.
These demonstrations wanted to draw again on a wide pool of public support after shocking images of escalating violence here caused many to rethink the direction of the pro-democracy push.
When it was announced inside an already full Victoria Park that underground train stations had been closed because too many people were flooding in trying to reach the rally, there was a huge cheer from the crowd.
Today has reinvigorated people's faith in this cause and, at the moment, made it feel like a decent proportion of this city's population are preparing to keep fighting right up to 2047, when Hong Kong is due to lose its special status and become a Chinese city like all others.
How have recent protests unfolded?
The violence has intensified in the past few weeks, and police have frequently fired tear gas and rubber bullets.
Last weekend activists occupied the airport, leading to hundreds of flights being cancelled. There were further clashes with police on Tuesday.
The turmoil has plunged one of Asia's leading financial centres into crisis. Many businesses remained closed on Sunday amid fears of further violence.
What is Beijing saying?
The Chinese government hardened its rhetoric following the airport unrest, condemning it as "behaviour that is close to terrorism".
It was the second time in a week that Chinese officials had publicly likened the protests to terrorist activity.
Some observers believe that the repeated use of such language suggests that China is losing patience with the protesters and signals that an intervention by Beijing is increasingly likely.
Thousands of armed police have been stationed across the border in Shenzhen.
"If Hong Kong's situation deteriorates to a point uncontrollable by the Hong Kong government, the central government will not sit by and watch," Chen Wen of the Chinese embassy in London told BBC Radio 4.
"We have enough powers and enough solutions to quell any unrest within the limit of basic law."
US President Donald Trump warned on Sunday that if China were to carry out a Tiananmen Square-style crackdown on the protesters, it would make a trade deal between Washington and Beijing "a very hard thing to do".
What is the movement about?
It was sparked by a bill that would allow extradition from Hong Kong to the Chinese mainland.
Critics argue that the proposal would undermine the territory's judicial independence and could be used to target those who speak out against the Chinese government.
The former British colony has a special status, with its own legal system and judiciary, and rights and freedoms not seen in mainland China.
The bill - announced by the government in February - was suspended following mass rallies in June. But the protesters want it withdrawn altogether.
Their current demands are:
- Complete withdrawal of the extradition bill
- The withdrawal of the "riot" description used about the 12 June protests
- An amnesty for all arrested protesters
- An independent inquiry into alleged police brutality
- Universal suffrage in elections for Hong Kong's chief executive (the city's leader), and Legislative Council.
Some also want the resignation of Carrie Lam, the current chief executive, whom they view as a puppet of Beijing.
More background on the protests
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