Chater Road, Jackson Road and Des Voeux Road Central were re-opened to traffic on Wednesday morning, but congestion warnings remain in place.

After 10am on Wednesday police announced that 511 people had been arrested on Chater Road on suspicion of illegal assembly and obstructing police officers in due execution of duty.

Arrests continued in central Hong Kong at least until 8am, the time protest leaders had aimed to continue the demonstration until.

When the clock struck 8, a cheer went up from the about 50 demonstrators left sitting in Chater Road as well as gathered supporters. The protesters then dispersed, with some arrests made.

Watch: Hong Kong police arrest hundreds of demonstrators at Chater Rd sit-in

The overnight protests followed a drawn-out July 1 march from Victoria Park to Central, in which organisers said 510,000 Hongkongers had taken part. Police said just 92,000 had completed the route.

After the march hundreds began a sit-in in Chater Road at midnight in what student leaders had said was a rehearsal for the civil disobedience movement Occupy Central.

Occupy organisers had discouraged participation in the protest, saying the government should be given time to put forward a plan for how the 2017 election should be held.

Another group of hundreds also marched to the chief executive’s office and debated with police over where they could set up camp to await Leung Chun-ying’s expected arrival at 8am.

Police accused of heavy-handed treatment of protesters

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The protesters on Chater Road spent the night sitting or lying on the ground, defying repeated police orders to leave the public space.

Media were also warned not to “obstruct” police or face prosecution.

At around 3am, about 500 demonstrators linked arms as police forcefully hauled away dozens.

Among the first to be targeted by police was student activist Tommy Cheung Sau-yin, who had been encouraging protesters using a megaphone.

Police corralled a group using metal barricades and begin to carry or drag them out – four officers per person – of the sit-in area.

Most protestors put up minimal resistance but continued chanting political slogans as they were taken away.

One protestor, an elderly woman, required one the wheelchairs that had been lined up near the protest site in preparation for the arrest of elderly demonstrators and those who refused to walk.

“The reason we are here is for universal suffrage and the future of our democracy,” one protestor shouted, as police officers regrouped and discussed their next move.

“We are here to protest the government not the police. You will regret this day for the rest of your lives,” the protester added.

Arrested demonstrators were ferried away to the Police College in Aberdeen by bus. It is the first time the site has been employed to handle mass arrests.

Some of the sit-in participants left on their own on police orders.

Three lawmakers – Albert Ho Chun-yan, Lee Cheuk-yan and Leung Yiu-chung – are among those arrested.

At about 7.30am, the chief executive arrived at his office in a Lexus car but did not stop at the gate, where more than 100 protesters continued to wait for him.

They chanted “CY Leung step down” as the car passed. Barricades and hundreds of police prevented them from getting near to the premises.

Joshua Wong, a prominent member of the student activist group Scholarism, one of the organisers of the overnight protests, called on demonstrators to clean up the protest sites and to go to the Police College to call for the release of demonstrators held there.

An 87-year-old man who gave the surname Tang was among those who had waited for the chief executive with Scholarism supporters.

“I came because I find Hong Kong increasingly ‘mainlandised’ since Leung Chun-ying took office,” he said.

“The white paper further sidelined ‘one country, two systems’ and I feel Hongkongers’ freedom is under threat.”

No arrests were reported outside the chief executive’s office.

A co-organiser of the Occupy Central movement, Dr Chan Kin-man, said on Wednesday morning that the rally in Chater Road had been peaceful and the use of force by police was disproportionate.

The protests’ dispersal ended Hong Kong’s largest pro-democracy demonstrations in a decade. Discontent had been fuelled by a central government white paper released last month in which Beijing asserted its control over the city.

Fears were raised that Hong Kong’s autonomy and independent judiciary could be under threat.

Estimates over how many people participated in the march overall varied widely. Organisers put the total at 510,000, while police estimated that only 98,600 participated at the peak of the march.

Police did not provide an estimate for the total number of participants in the largely peaceful march.

The University of Hong Kong’s public opinion programme put the turnout at between 154,000 and 172,000.

The march followed an unofficial referendum on options for the 2017 election, organised by Occupy Central last week, in which almost 800,000 people voted.

However, Beijing's top official in Hong Kong, liaison office director Zhang Xiaoming , said in Beijijng on Tuesday that neither the march or the referendum would affect the central government's determination to implement universal suffrage "in accordance with the law".

"What we firmly oppose are illegal acts by an extremely small group of people," Zhang said.

On Wednesday morning, congestion warnings were raised in Admiralty and Central, and drivers were asked to avoid the areas unless “necessary” by transport bosses.