HONG KONG, July 2 (Reuters) - Hundreds of police started removing protesters from the heart of Hong Kong's business district early on Wednesday as they tried to stage a sit-in after a rally to demand greater democracy.
The pro-democracy march, which organisers said attracted more than 510,000 people, and the subsequent sit-in by mainly student groups could turn out to be the biggest challenge to Chinese Communist Party rule in more than a decade.
Police surrounded protesters sitting on Chater Road, close to the city's Legislative Council building, warning them their assembly was "unauthorised" and that police would use force to remove them if necessary.
"I have the right to protest, we don't need police permission," the crowd chanted as they sat sweltering in Hong Kong's summer heat and humidity.
Some elderly residents were among the protesters, who numbered more than a thousand in the early hours of Wednesday.
One police officer gave activists a 10-minute warning to evacuate the area, saying failure to do so may render them liable to arrest and prosecution.
Police moved in quickly and started carrying people away. Many protesters linked arms in a bid to resist police efforts to remove them but they were taken away one at a time, in some cases by three or four officers, as activists kicked, screamed and punched their fists, before being bundled onto coaches.
One man took to a stage and shouted: "The whole world will know how ugly the Hong Kong police is."
The protest threatened to disrupt traffic in the heart of the business district as people were set to return to work on Wednesday following a public holiday on Tuesday to mark the 17th anniversary of Hong Kong's return to China.
Some buildings in the area, including HSBC's headquarters, were ringed by barriers.
The demonstrators are demanding greater democracy in elections for the city's leader, or chief executive, in 2017. They want nominations to be open to everyone. China's leaders want to ensure only pro-Beijing candidates are on the ballot.
Hong Kong Chief Executive Leung Chun-ying said his government would do its "utmost" to move towards universal suffrage and stressed the need for stability after nearly 800,000 people voted for full democracy in an unofficial referendum last month.
(Reporting By Clare Baldwin and James Pomfret; Writing by Anne Marie Roantree; Editing by Janet Lawrence)