The occupation came as tens of thousands of people gathered in nearby Tamar Park for a rally to mark the start of the 2014 pro-democracy campaign.
Bricks were ripped up from a pavement and ferried in metal drums to those protesters closest to a group of riot police by the government complex.
The bricks were hurled towards the riot officers, who were some distance away behind water barriers, as well at windows of the government building.
A helicopter circled above the area at one point, with some people shining laser pointers at it. There was also an intense light show going on outside the People’s Liberation Army building.
At around 8pm, a police water cannon vehicle was brought close to the protesters from inside the government complex, with sudden cries all round for umbrellas to be rushed to those at the frontline.
Police officers also fired a pepper spray based solution at some of the crowd.
Soon after raising the red and black warning flags, officers started firing the water cannon as well as tear gas in a bid to disperse the demonstrators.
The crowd moved back but did not scatter immediately. After a while though, there were calls for people to leave and many began heading towards Wan Chai, and later, back towards Central.
Some protesters were seen changing out of their signature black clothing into t-shirts of various colours, and it appeared that most heeded pleas for them to call it a night and to conserve their energy for planned protests on October 1.
Riot police were seen in a number of MTR stations and people in the crowd urged others not to risk going home by train.
Traffic on both sides of Harcourt Road had been very quickly brought to a standstill when the blockade began shortly before 7.30pm.
One motorist caught up the drama told RTHK he wasn’t bothered about the inconvenience caused by the action and what the protesters were doing was more important than his journey.
But a taxi driver said he was too afraid to speak to the press, in case the protesters beat him up.
Even before the rally had got underway shortly after 7pm, riot police had fired pepper spray at a group of protesters who they said had been shining laser pointers at them outside the entrance of the Central Government Complex.
After the rally ended around half an hour early at 8.30pm, a group of protesters also occupied Lung Wo Road for some time before leaving in the direction of Central after police sprayed them with jets of water.
Last updated: 2019-09-28 HKT 21:48