Pro-democracy activists and police have clashed in Hong Kong, as thousands of people tried to surround government headquarters overnight.
Protesters fought police armed with pepper spray and batons on roads around the two-month-old protest camp in the Admiralty district.
Police say 45 people have been arrested and a number of officers have been injured.
It is some of the worst violence since the protests began in late September.
The protesters want the people of Hong Kong to be allowed to choose their leaders in the 2017 elections without interference from Beijing. The Chinese government has said it will allow universal suffrage, but will screen candidates for the chief executive post in advance.
Last week police and court bailiffs removed one of the major protest camps in the Mong Kok commercial district.
The unrest flared overnight, after student leaders of the protest movement called on supporters to converge on the offices of Chief Executive CY Leung, a short distance away from Connaught Road, the major road they have been occupying for two months.
Protesters, many wearing hard hats, moved into the area, carrying umbrellas - the symbol of their movement - and throwing missiles towards police.
Many activists chanted: "I want true democracy!"
Police ordered them to retreat, then charged protesters, eventually forcing them out of the area.
"The action was aimed at paralysing the government's operation,'' student leader Alex Chow was quoted by the Associated Press as saying.
"The government has been stalling... and we believe we need to focus pressure on the government headquarters, the symbol of the government's power.''
Last week more than 100 people - including some key protest leaders - were arrested as the Mong Kok camp, across the harbour from Admiralty, was dismantled.
The latest clashes come after China said it would not allow a UK parliamentary committee to enter Hong Kong as part of an inquiry into British relations with its former colony.
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