A top Chinese official has issued a stark warning to Hong Kong protesters, saying “those who play with fire will perish by it”, while local media report that 12,000 police performed anti-riot drills near the border.

Yang Guang, a spokesperson for China’s Hong Kong and Macau Affairs Office, said the protests are pushing the city towards a “dangerous abyss” and punishment is “only a matter of time”.

In the latest hint that the Chinese government will take a hard line in Hong Kong, Mr Yang said in a document released before a briefing in Beijing: “I would like to warn all of the criminals: don’t ever misjudge the situation and mistake our restraint for weakness.

“At the end of the day, [protesters] will eventually be punished.”

The document singled out a group of “violent criminals” at the front of the protests with “some kind-hearted citizens who have been misguided and coerced to join”.

Hong Kong protesters hit with tear gas shot by riot police Show all 16 1 /16 Hong Kong protesters hit with tear gas shot by riot police Hong Kong protesters hit with tear gas shot by riot police Police fire tear gas on protesters in Hong Kong AP Hong Kong protesters hit with tear gas shot by riot police The protesters removed a Chinese national flag from its pole and flung it into the city's iconic Victoria Harbour and police later fired tear gas at demonstrators after some of them vandalized a police station AP Hong Kong protesters hit with tear gas shot by riot police Protesters burn cardboard to form a barrier AP Hong Kong protesters hit with tear gas shot by riot police Protests take cover from the tear gas shot by riot police EPA Hong Kong protesters hit with tear gas shot by riot police Riot police in protective gear AP Hong Kong protesters hit with tear gas shot by riot police Police fire tear gas during a protest in Tsim Sha Tsui district in Hong Kong on August 3, 2019. - Anti-government protesters in Hong Kong erected barricades in a popular shopping district and blocked a major tunnel on the evening of August 3, defying increasingly stern warnings from China over weeks-long unrest that has plunged the city into crisis. (Photo by Philip FONG / AFP)PHILIP FONG/AFP/Getty Images PHILIP FONG AFP/Getty Hong Kong protesters hit with tear gas shot by riot police An anti-extradition bill protester is covered in tear gas during a march in Hong Kong, China, August 3, 2019. REUTERS/Eloisa Lopez ELOISA LOPEZ Reuters Hong Kong protesters hit with tear gas shot by riot police Police fire tear gas during a protest in Tsim Sha Tsui district in Hong Kong on August 3, 2019. - Anti-government protesters in Hong Kong erected barricades in a popular shopping district and blocked a major tunnel on the evening of August 3, defying increasingly stern warnings from China over weeks-long unrest that has plunged the city into crisis. (Photo by Philip FONG / AFP)PHILIP FONG/AFP/Getty Images PHILIP FONG AFP/Getty Hong Kong protesters hit with tear gas shot by riot police Protesters burn cardboard to form a barrier as they confront with police in Hong Kong on Saturday, Aug. 3, 2019. Hong Kong protesters removed a Chinese national flag from its pole and flung it into the city's iconic Victoria Harbour on Saturday, and police later fired tear gas at demonstrators after some of them vandalized a police station. (AP Photo/Kin Cheung) Kin Cheung AP Hong Kong protesters hit with tear gas shot by riot police epa07754951 A protests take cover from the tear gas shot by riot police as anti-extradition bill protesters gather outside Tsim Sha Tsui police station during a rally in Hong Kong, China 03 August 2019. Hong Kong is bracing itself for a ninth consecutive weekend of multiple anti-extradition demonstrations and a planned citywide strike on 05 August. EPA/JEROME FAVRE JEROME FAVRE EPA Hong Kong protesters hit with tear gas shot by riot police Protesters shine a laser beam as they form up in gas masks and umbrellas during a confrontation with police in Hong Kong on Saturday, Aug. 3, 2019. Hong Kong protesters removed a Chinese national flag from its pole and flung it into the city's iconic Victoria Harbour on Saturday, and police later fired tear gas at demonstrators after some of them vandalized a police station. (AP Photo/Vincent Thian) Vincent Thian AP Hong Kong protesters hit with tear gas shot by riot police epa07754995 Riot police shoot tear gas against anti-extradition bill protesters gathered outside Tsim Sha Tsui police station during a rally in Hong Kong, China, 03 August 2019. Hong Kong is bracing itself for a ninth consecutive weekend of multiple anti-extradition demonstrations and a planned citywide strike on 05 August. EPA/JEROME FAVRE JEROME FAVRE EPA Hong Kong protesters hit with tear gas shot by riot police Riot police in protective gear run forward during a confrontation with protesters in Hong Kong on Saturday, Aug. 3, 2019. Hong Kong protesters removed a Chinese national flag from its pole and flung it into the city's iconic Victoria Harbour on Saturday, and police later fired tear gas at demonstrators after some of them vandalized a police station. (AP Photo/Vincent Thian) Vincent Thian AP Hong Kong protesters hit with tear gas shot by riot police Anti-extradition bill protesters walk among tear gas as they attend a march in Hong Kong, China, August 3, 2019. REUTERS/Kim Kyung-Hoon KIM KYUNG-HOON Reuters Hong Kong protesters hit with tear gas shot by riot police Police fire tear gas during a protest in Tsim Sha Tsui district in Hong Kong on August 3, 2019. - Anti-government protesters in Hong Kong erected barricades in a popular shopping district and blocked a major tunnel on the evening of August 3, defying increasingly stern warnings from China over weeks-long unrest that has plunged the city into crisis. (Photo by Philip FONG / AFP)PHILIP FONG/AFP/Getty Images PHILIP FONG AFP/Getty Hong Kong protesters hit with tear gas shot by riot police Riot police form up as journalists work nearby amongst tear gas in Hong Kong on Saturday, Aug. 3, 2019. Hong Kong protesters removed a Chinese national flag from its pole and flung it into the city's iconic Victoria Harbour on Saturday, and police later fired tear gas at demonstrators after some of them vandalized a police station. (AP Photo/Vincent Thian) Vincent Thian AP

It also claimed unspecified anti-China forces were behind the protests, accusing them of being “behind-the-scenes masterminds” who had “openly and brazenly emboldened” the protesters.

China has been quick to label US officials as “black hands” instigating unrest in Hong Kong to contain China’s development, but it has not provided any concrete evidence.

Meanwhile, some 12,000 police officers performed anti-riot drills in the nearby city of Shenzhen, just across the border of the special administrative region, the South China Morning Post reported on Tuesday.

Chinese police said on popular Chinese networking platform Weibo that the drill was designed to “increase troop morale” and “maintain national political security and social stability” ahead of the celebrations for the 70th anniversary of the People’s Republic of China on 1 October.

But observers noticed that the drills had unmistakable similarities to the Hong Kong protests.

Officers wore body armour and shields and confronted people wearing black clothes, breathing masks and safety helmets, all of which have become typical among protesters.

Last week, China’s People’s Liberation Army (PLA), stationed in Hong Kong, posted a video of soldiers performing similar drills.

The army has remained in barracks during the protests, leaving the police to deal with the protests, but Mr Yang seemed to hint that it could become involved.

He called the PLA “a strong force that defends every inch of its sacred territory”, and said the central government would not allow any “turbulence” beyond the control of the Hong Kong government to threaten national unity or security.

Chaos in Hong Kong's Yuen Long as van almost crashes into protesters building barricades in road

Diplomats and foreign security analysts believe there is little appetite in Beijing to deploy the PLA in Hong Kong.

But the actions appear to be a sign that China has no intention of opening a dialogue with protesters.

Protesters held a televised news conference on Tuesday asking again that the government respond to their demands.

These include the complete withdrawal of the extradition bill, ceasing to describe the demonstrations as riots, the resignation of chief executive Carrie Lam and an independent inquiry into suspected police violence.

“We call on the government to return the power back to the people and to address the demands of Hong Kong citizens,” the protesters said, declining to give their real names.

They said the group “was not affiliated with any political party or organisation” and apologised for the inconvenience caused by a general strike that paralysed the city on Monday.

Police on Monday fired tear gas at protesters after the strike blocked major roads and public transit lines and caused at least 77 flights to be cancelled.

The protests started over an extradition bill that would have allowed people to be sent to mainland China for trial but have now turned into broader unrest against the city’s government and the central government of China.

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Hong Kong was once a British colony but was returned to China in 1997 under the “one country, two systems” framework, which stated that the region would retain democratic freedoms that are not seen on the mainland for 50 years.

But many residents fear that freedoms are being eroded under the control of the Chinese Communist Party.