Hong Kong police used tear gas Sunday and warned of further measures as they tried to clear thousands of pro-democracy protesters who had gathered outside government headquarters in a challenge to Beijing over its decision to restrict democratic reforms for the semiautonomous city.

After spending hours holding the protesters at bay, police lobbed canisters of tear gas into the crowd on Sunday evening. The searing fumes sent demonstrators fleeing down the road, but many came right back to continue their protest.

Students and activists have been camped out on the streets outside the government complex since late Friday. Students started the rally, but by early Sunday leaders of the broader Occupy Central civil disobedience movement said they were joining them to kick-start a long-threatened mass sit-in to demand that an election for Hong Kong’s leader be held without Beijing’s interference.

Police used the tear gas after the protest spiraled into an extraordinary scene of chaos, with the demonstrators jamming a busy road and clashing with officers wielding pepper spray.

The protesters were trying to reach a mass sit-in being held outside government headquarters to demand Beijing grant genuine democratic reforms to the former British colony.

“It was very cruel for the police to use such harsh violence on protesters who had been completely peaceful,” said one of the demonstrators, Cecily Lui, a 30-year-old clerk. “They were just sitting down on the road asking to speak with (Hong Kong leader) Leung Chun-ying to start a dialogue. Now, police have solved nothing and students are more resolved to stay.”

After using the tear gas, police issued a statement urging the protesters to “leave peacefully and orderly.”

“Otherwise police will use a higher level of force in order to restore public order and safeguard public safety,” the statement warned.

The demonstrations — which Beijing called “illegal” — were a rare scene of disorder in the Asian financial hub, and highlighted authorities’ inability to rein in the public discontent over Beijing’s tightening grip on the city. The protesters reject Beijing’s decision last month to rule out open nominations for candidates under proposed guidelines for the first-ever elections for Hong Kong’s leader, promised for 2017.

China took control of the former British colony in 1997, agreeing to a policy of “one country, two systems” that allowed Hong Kong to keep civil liberties unseen on the mainland, while promising that the city’s leader can eventually be chosen through “universal suffrage.” But Beijing’s insistence on screening election candidates for patriotism to China has stoked fears among democracy groups that Hong Kong will never get genuine democracy.

Earlier Sunday, thousands of protesters who tried to join the sit-in breached a police cordon, spilling out onto a busy highway and causing traffic to come to a standstill.

Police officers in a buffer zone manned barricades and doused the protesters with pepper spray carried in backpacks. The demonstrators, who tried at one point to rip apart metal barricades, carried umbrellas to deflect the spray by the police, who were wearing helmets and respirators.

Police had told those involved in what they also call an illegal gathering to leave the scene as soon as possible, warning that otherwise they would begin to clear the area and make arrests.

After police used the tear gas, the protesters chanted “Shame on C.Y. Leung,” referring to the city’s deeply unpopular Beijing-backed leader. To many, it seemed to mark a major shift for Hong Kong, whose residents have long felt their city stood apart from mainland China thanks to its guaranteed civil liberties and separate legal and financial systems.

Hong Kong “has changed to a new era so the people have to be awakened. It’s no longer the old Hong Kong,” said one protester, W.T. Chung, 46, who yelled at police officers after they used the tear gas.

Earlier, police said they had arrested 78 people since demonstrations started late Friday, though all but three were released.

Leung said Hong Kong’s government was “resolute in opposing the unlawful occupation” of the government offices or the financial district by Occupy Central.

“The police are determined to handle the situation appropriately in accordance with the law,” he said at a news conference.

The Chinese government agency that handles Hong Kong affairs condemned the protests.

“China’s central government firmly opposes illegal acts taking place in Hong Kong,” and fully supports the local government in handling the matter according to the law, the official Xinhua News Agency quoted the Hong Kong and Macau Affairs Office of the State Council as saying.

Protest organizers said police took away several pro-democracy legislators who were among the demonstrators.

Among the protesters was media magnate Jimmy Lai, who owns the popular Apple Daily, Hong Kong’s sole pro-democracy newspaper.

(AP)