Crowds remained on the streets overnight after a day that saw riot police deploy tear gas and batons in a bid to disperse them.
On Monday, the Hong Kong government said riot police were being withdrawn as people had "mostly calmed down".
But some banks and schools were closed, and there was transport chaos.
Protesters - a mix of students and supporters of the Occupy Central pro-democracy movement - are angry at Beijing`s plans to vet candidates for Hong Kong`s 2017 leadership elections.
They want a free choice of candidates when they cast their ballots for the chief executive - something Beijing says is out of the question.
Sunday saw angry scenes and dozens of arrests on Hong Kong`s streets as tens of thousands of protesters faced riot police in the heart of the city.
Many of them remained camped out around the government complex overnight, some erecting barricades.
About 3,000 people have also blocked a major road across the bay in Mongkok while a crowd of about 1,000 faced police in the busy shopping district of Causeway Bay, east of central Hong Kong.
Overnight, Hong Kong`s chief executive reassured the public that rumours the Chinese army might intervene were untrue.
"I hope the public will keep calm. Don`t be misled by the rumours," CY Leung said.
The government urged protesters to stay calm and leave peacefully.
Schools in three districts have been closed and the city remains heavily disrupted, with several major thoroughfares blocked.
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