Media playback is unsupported on your device Media caption The BBC's China Editor Carrie Gracie: "As night fell the crowd swelled"

Protests in Hong Kong are continuing after tens of thousands of people defied calls for them to dismantle their camps and return home.

Demonstrations grew after police tried to disperse crowds using batons and tear gas in the early hours of Monday morning. Riot police later withdrew.

The pro-democracy protesters are angry at China for limiting their choice in Hong Kong's 2017 leadership elections.

China has warned other countries not to support the "illegal rallies".

The protesters - a mix of students and members of the Occupy Central civil disobedience movement - want Beijing to abandon its plans to vet candidates for the post of chief executive in the 2017 polls.

They want a free choice of candidates. Until now the territory's chief executive has essentially been selected under a pro-Beijing mechanism.

Response from West

On Monday, the British government called for the right to protest to be protected and for protesters to exercise their right within the law.

That call was echoed by the US, with White House spokesman Josh Earnest calling on Hong Kong's authorities to show restraint.

"The United States supports universal suffrage in Hong Kong in accordance with the Basic Law and we support the aspirations of the Hong Kong people," Mr Earnest told reporters.

Image copyright Getty Images Image caption The protesters are calling on Beijing to grant them fully democratic elections in 2017

Image copyright Getty Images Image caption Correspondents said the demonstrators were tired after several days of protests but remained defiant

Image copyright AFP Image caption The police force stood off from protesters on Monday night after being criticised for their actions on Sunday

At the scene: Martin Patience, BBC News, Hong Kong

As night fell, cheers rippled through the crowd. Many office workers joined the protesters or stood on bridges watching the remarkable scenes.

The only jeering I heard was when protesters held up a huge portrait of Chief Executive CY Leung and carried it through the crowd.

For the demonstrators he is now Public Enemy Number One and they have called on him to resign.

Many other people in Hong Kong are not on the streets and think the protesters are pushing their luck with Beijing. They also fear that growing protests could lead to instability, and the possible flight of capital.

Beijing's tricky balancing act

Dozens of protesters were arrested overnight on Sunday amid angry scenes that saw riot police fire tear gas into large crowds.

Cheung Tak-keung, assistant commissioner of police for operations, insisted police had used the "bare minimum force".

He said 41 people, including 12 police officers, had been injured since protests broke out.

The Hong Kong government urged protesters to stay calm and leave peacefully but crowds remained camped out around the government complex on Monday night.

Thousands of people blocked a major road across the bay in Mongkok, on the Kowloon peninsula, while another large crowd brought the busy shopping district of Causeway Bay, east of central Hong Kong, to a standstill.

Media playback is unsupported on your device Media caption China editor Carrie Gracie asks protesters about the financial implications

Schools in the Wan Chai, Central and Western districts were closed on Monday and will remain shut on Tuesday, according to the Hong Kong Education Bureau.

The city remains heavily disrupted, with several major thoroughfares blocked.

Tensions escalated on Sunday when Occupy Central threw its weight behind student-led protests, bringing forward a mass civil disobedience campaign due to start on Wednesday.

The movement called on CY Leung, the current chief executive, to step down, saying "only this will make it possible to re-launch the political reform process and create a space in which the crisis can be defused".

Media playback is unsupported on your device Media caption Chief Executive CY Leung said the protests were an "unlawful occupation"

Chinese media have blamed "radical opposition forces" for stirring up trouble.

Analysts say Communist Party leaders in Beijing are worried that calls for democracy could spread to cities on the mainland.

Britain handed Hong Kong back to China in 1997 under a "one country, two systems" formula that guarantees liberties not seen on the mainland, including freedom of speech and the right to protest.

Hong Kong democracy timeline

1997: Hong Kong, a former British colony, is handed back to China under an 1984 agreement giving it "a high degree of autonomy, except in foreign and defence affairs" for 50 years

2004: China rules that its approval must be sought for changes to Hong Kong's election laws

June-July 2014: Pro-democracy activists hold an unofficial referendum on political reform and a large rally. This is followed by protests by pro-Beijing activists

31 August 2014: China says it will allow direct elections in 2017, but voters will only be able to choose from a list of pre-approved candidates. Activists stage protests

22 September 2014: Student groups launch a week-long boycott of classes in protest

2017: Direct elections for chief executive due to take place

2047: Expiry of current agreements

Q&A: Hong Kong's democracy controversy