Thousands of people joined the protest demanding electoral reforms outside the Tamar complex that houses the office of the chief executive of Hong Kong, the legislative council and central government offices, the South China Morning Post reported, adding that police arrested 13 protesters Saturday morning and 61 more in the afternoon.
Police and protesters outside the government headquarters appeared to be ready for a showdown, as more officers started to pour inside.
Barricades were erected to keep the protesters away, as a police spokesperson said the gathering was an "act of unlawful assembly".
"Police urge people, especially students and those underage, not to join the unlawful assembly. If unnecessary, don’t pass through or get near the area,” he said.
Police earlier announced that four officers and 11 government headquarters employees had sustained injuries during the demonstration. No official count of protesters’ injuries was released.
Hong Kong Federation of Students convenor Gary Fong Chi-shun said around eight of its members had been arrested.
Reports said the number of people had swelled at the protest site and that the groups were becoming more organised and were discussing how they would deal with further police action.
The week-long class boycotts by university students ended Friday night in chaos as about 200 protesters broke into the civic square outside the government headquarters. Clashes broke out between police officers and protesters in which several students were injured.
Officers armed with helmets and shields forced their way out of the government headquarters Saturday morning to clear demonstrators staging a sit-in on Tim Mei Avenue.
Police announced that dozens of protesting students, who had been surrounded by metal barricades since they broke in Friday night, would be removed and arrested.
Police used pepper spray on protesters and many appeared to be hit in the face. Some protesters were seen throwing plastic bottles back at officers.
The students appeared to be calm and chanted the slogan: "No fear for civil disobedience". They were escorted one after another, without resisting arrest, with the last of the protesters led away by police just before 2 p.m.
A civil disobedience campaign was launched Aug 31 in response to the decision by the Permanent Committee of the Chinese People's Assembly to approve universal suffrage for the Hong Kong government elections in 2017 but to only allow two or three candidates previously selected by a special government commission of 1,200 members to run for each post.
Saturday's demonstrations were the latest in a series of confrontations between democracy supporters and those who support the Chinese government's decisions on how to carry out electoral reforms in Hong Kong.
During the transfer of control over Hong Kong from the British to the Chinese government in 1997 under the "one country, two systems" brand of government, it was established -- without specifying a date -- that universal suffrage would be implemented in the city.