HONG KONG - Hong Kong on Wednesday (Nov 13) faced a third straight day of traffic chaos as protesters continued their strike, obstructing roads and fighting pitched battles with police across the city as schools cancelled classes.

The Education Bureau announced that all schools including kindergarten, primary and secondary as well as special schools will suspend lessons on Thursday (Nov 14) out of safety concerns.

The Hong Kong Association of the Heads of Secondary Schools has asked the Education Bureau to suspend school on Friday as well.

"In some schools situated under the impact of confrontational events, teachers and students had their lessons amidst the tear gas," the association was cited by South China Morning Post as saying.

Chief Executive Carrie Lam had noted, on Monday, that masked protesters were obstructing traffic in a bid to paralyse the city, and if the government suspended school or other activities, it will "fall into the protesters' trap, and give the impression that the city has come to a standstill".

She said the people in Hong Kong wanted to continue with their daily lives - go to school, go to work.

The Chinese University of Hong Kong (CUHK) - the site of violent clashes between police and students - will cancel all of its on-campus classes until the end of November.

There were chaotic scenes through the night at CUHK, where pitched battles raged, students continued manning barricades they had built, many spending the night in the open on the running track and sports field amid fears that police could storm the school or hostels to arrest protesters.

Officers had beat a retreat from the campus on Tuesday night, after spending about 15 hours battling protesters who had built barricades and started fires. Police had fired tear gas and rubber bullets to try to disperse the students.

"Despite multiple attempts to coordinate and negotiate with both parties made by the Vice-Chancellor and senior management, the negotiation ultimately failed due to sustained confrontation," Chinese University said in a statement on Wednesday evening.

"Upon learning of the arrest of CUHK students yesterday, Professor Rocky S. Tuan, Vice-Chancellor and President of CUHK, went to the police station to visit the arrested students. Three students were subsequently released on bail and provided medical and legal assistance," it said.

"The University will continue to provide appropriate assistance to other injured members of the University," it added.

Chief Superintendent John Tse of the police public relations branch said that what happened at the Chinese University is a bad omen for Hong Kong.

"A university is supposed to be a breeding ground for future leaders, but it became a battlefield for criminals and rioters," Tse said.

"What's worse, we have strong suspicions that the school was used as a weapons factory as several hundred petrol bombs were thrown on campus in a single day," he added.

CUHK's student union president Jacky So lodged an urgent bid in the High Court on Wednesday morning to stop police from entering the university's campus in Sha Tin.

The injunction will also prevent police from using crowd control weapons, such as tear gas and rubber bullets in the university.

Mr So criticised the police, accusing them of using excessive force against students.

At the Hong Kong Polytechnic University in Hung Hom, protesters too built barricades to disrupt traffic going into the busy Cross Harbour Tunnel.

At least 11 tertiary institutions, including the City University, the Open University, University of Hong Kong, University of Science and Technology, and Hong Kong Polytechnic University, have said that classes will be suspended.

At noon on Wednesday, hundreds heeded calls to gather on the streets of the Central financial district, many dressed in office attire. As they shouted protest slogans, demonstrators built barricades on several main roads using traffic cones, plastic crates and even rocks.

For the third day in a row, people gathered at the junction of Des Voeux Road Central and Pedder Street in Central. Bricks littered the road, blocking traffic.

Riot police deployed to the financial district took swift action to arrest protesters in Exchange Square and in the vicinity.

As they moved in, the largely office crowd got angry and shouted at the officers to release those arrested.

Two entire MTR lines have been shut because of disruptions and objects tossed onto tracks, while numerous stations have also been shut

Livestream footage on TVB television broadcasting company showed crowded platforms at Tiu Keng Leng MTR station and a packed train stalled with its door open.

Rail operator MTR Corporation said it would not provide bus services because of "adverse road conditions". Demonstrators have been seen building barricades on several major roads to cripple traffic, tossing bricks and other obstacles.

By morning, many roads were littered with debris as people heeded overnight calls on messaging forums to hit their local neighbourhoods to stretch police resources and keep them distracted from CUHK.

In Mong Kok, the usually busy shopping district that has become a flashpoint in recent weeks, the streets were littered with debris from overnight battles that had lasted till 5am on Wednesday.

Chief Secretary Matthew Cheung said ahead of a Legislative Council sitting on Wednesday: "Whatever your motives are, violence, attacking others will not get you want you want." He was joined by the security, transport and education secretaries.

Secretary for Security John Lee defended the police's use of force the day before, saying that they had to secure a bridge in CUHK because protesters were throwing objects off the bridge onto a main thoroughfare below.

"When something like that is so outrageously dangerous, of course they must take action. That's what we saw on television. We need to put things into perspective… when we look at this incident," he said.

In a joint statement issued before lunch, the Colloquium of six religious leaders of Hong Kong called for peace and harmony. It said no one should preach violence in their fight for demands, while the police should "exercise force legally and keep restraint".

"The government should actively consider solutions to relieve public grievances in order to calm the society as soon as possible," it added.

Hong Kong has been hit by five months of unrest that was sparked by a contentious extradition Bill that would have allowed the handover of fugitives to several jurisdictions, including mainland China. The protests have since evolved into calls for democracy and an outpouring of anger against the local government.

Hong Kong's stock market dropped 2 per cent to a three-week low in early trade on Wednesday, outpacing falls elsewhere in Asia.

The drop came after the city's embattled leader, Mrs Lam, said protesters trying to paralyse the city were being "extremely selfish".

Chinese state media condemned the violence, with the official Xinhua news agency writing in a commentary that Hong Kong is at "the most critical juncture", as the violent acts of "black-clad rioters" are close to that of terrorism.

Many people in Hong Kong have already been "swept into a morbid state of bipolarism" over months of protest, it said, warning that "if this kind of oddity was allowed to continue, society would be left with little time to correct itself".

"Dialogue can happen when there are political differences, but on matters of principle such as stopping chaos and violence, and the future of Hong Kong, all Hong Kong people should be united in saying no to violence," the commentary said.

The China Daily newspaper stated young protesters were revelling in a "hormone-fuelled 'rebellion'".

"It is foolish and naive to believe that Hong Kong would be better off by eliminating all mainland factors. Particularly, since the mainland is the main source of fresh water, electricity and the largest supplier of food to the city."

The chairman of the United States Senate Foreign Relations Committee said on Tuesday that he wanted the Senate to pass legislation to support pro-democracy protesters in Hong Kong.

Republican Senator Jim Risch noted that he is a co-sponsor and "strong proponent" of the Hong Kong Human Rights and Democracy Act, which would place Hong Kong's special treatment by the US under tighter scrutiny.

"We want it moved," Mr Risch said during a discussion on China at the Centre for Strategic and International Studies in Washington.

What started as mostly peaceful rallies have turned increasingly violent, with Monday seeing some of the worst violence in the former British colony in decades after a man was set on fire and a protester was shot at close range.

Defending their actions in the Monday shooting incident, police on Tuesday said the officer had been confronted by a group of protesters who attempted to steal his gun.

"As we gathered the statement from the man who was injured (by gun shot), we found out that our colleague did not only face threat from one person, instead it was a group of people with an organised plan attempting to steal the gun," said senior superintendent of organised crime and triad bureau Li Kwai Wah.

"In a situation like this, we believe our police are reacting according to the guideline, to protect themselves as well as the people around them."