Protest movement urges all those who want to make their feelings known to Beijing to join in ‘defining moment’ for territory

Thousands of pro-democracy protesters paralysed parts of Hong Kong’s central business district on Sunday, as police in riot gear attempted to disperse them with teargas and pepper spray.

Using a park near the Hong Kong government headquarters as a base, the protesters have blocked many of the city’s main thoroughfares, forcing authorities to divert about 80 bus routes. Organisers say at least 30,000 people have joined the demonstration.

Police fired volleys of teargas into the crowds at least three times on Sunday afternoon, according to reports posted online, sending protesters running and pleading for water and paper towels. Police have threatened to use a “higher degree of force” if the demonstrators do not disperse.

Facebook Twitter Pinterest Riot police fire pepper spray against protesters near government headquarters in Hong Kong. Photograph: Vincent Yu/AP

Alvin Au, a teacher who said he had been at the protest all day to keep an eye on his teenage students, told the Guardian: “We all saw the teargas. None of us expected they would use it. It’s beyond our imagination and toleration. We Hong Kongers have to strike for the common good. The government is becoming irrational.”

At least 34 people have been injured since the protest began, including four police officers and 11 government staff and guards, authorities said. One officer suffered a gash after being poked by an umbrella used to deflect pepper spray.

The movement’s leader, Benny Tai, expressed surprised at the surge in support. “It is totally unexpected,” he said, according to the South China Morning Post. “It’s all about our pursuit of democracy. Beijing now sees it; the world now sees it; [chief executive] CY Leung, do you see it?”

China runs the former British colony separately from the mainland under the “one country, two systems” framework.

Beijing has promised universal suffrage for the election of its chief executive from 2017, but reformers are angry about restrictions that have been imposed on the process, including tight control of candidates by a nomination committee stacked with pro-Beijing loyalists.

Facebook Twitter Pinterest Protesters teargas fired by riot police. Photograph: Reuters

The protesters had hoped the threat of action might persuade Beijing to compromise, but the details of the decision underlined their fears that Hong Kong’s identity and autonomy are gradually being eroded.

The protesters have been camped outside of the government complex in central Hong Kong all weekend. Students started the rally, but by early Sunday leaders of the broader Occupy Central movement said they were joining them to kickstart a long-threatened mass sit-in.

Demonstrators barricaded themselves inside the protest zone using metal crowd-control barriers originally brought in by authorities. They donned protective gear in case police used pepper spray, wrapping their faces and arms with clingfilm and wearing cheap plastic raincoats, goggles and surgical masks.

The arrest of several student leaders first brought supporters on to the streets after around 150 demonstrators broke through police lines and stormed the city headquarters late on Friday night. Three well-known activists were still being held on Sunday morning.

Police used pepper spray as they struggled to clear demonstrators from the scene overnight, but late on Saturday large crowds gathered around the complex to support the student protesters, who had been boycotting classes all week.

Occupy Central had originally planned to take over the financial district from Wednesday, a national holiday.

Facebook Twitter Pinterest A protester wears clingfilm over an eye mask to protect against pepper spray. Photograph: Alex Ogle/AFP/Getty Images

“The two nights of occupation of Civic Square in Admiralty have completely embodied the awakening of Hong Kong people’s desire to decide their own lives,” the group said in a statement. “The courage of the students and members of the public in their spontaneous decision stay has touched many Hong Kong people. Yet, the government has remained unmoved … We have decided to arise and act.

“We reiterate we will stand firm in our belief in peace and non-violence. We urge Hong Kong people to respond to the call of history, to stand up and have the courage to be a real Hong Kong citizen.”

Its demands are for the withdrawal of Beijing’s decision on the framework for Hong Kong’s political reform, and a resumption of political reform consultations.

Media outlets have reported that many of those outside the government headquarters left the scene after Occupy Central’s statement, although more than 1,000 remained there overnight as hundreds of police officers watched.

Facebook Twitter Pinterest A protester clings to a barrier fence clashes with riot police. Photograph: Tyrone Siu/Reuters

“A lot of students left as soon as Occupy made the announcement they were starting their occupation,” said Vito Leung, a recent graduate.

“I think they were really forcing it. This was always a separate student movement with similar goals but different directions. I don’t think it should be brought together like this,” added Leung, who vowed to stay until police released Joshua Wong, the prominent 17-year-old leader of the activist group Scholarism.

Wong was among the first to be arrested as protesters charged the government complex on Friday night, and was still being detained early on Sunday, along with fellow student leaders Alex Chow and Lester Shum. His parents said in a statement that his detention was an act of “political persecution”.

The Civic party leader Alan Leong told the South China Morning Post that 18 pan-democrat MPs, including himself, would take part in the sit-in. “[Some protesters] may not want to support Occupy and have left, but all Hong Kongers who want their attitude known to the Communist party [should come] because this is a defining moment of Hong Kong,” he said.

The publishing tycoon Jimmy Lai, an outspoken critic of Beijing and backer of democracy activists, said: “Whoever loves Hong Kong should come and join us. This is for Hong Kong’s future.”