Hong Kong has suffered more than eight weeks of protests that began with opposition to a now-shelved extradition bill that would have allowed suspects to be tried in mainland courts.
But now these demonstrations have evolved into a catch-all movement against the local government and are causing disruptions.
The protesters are now demanding an independent inquiry into the police violence, resignation of the territory's Chief Executive Carrie Lam and democratic reform.
Yang Guang, a spokesman for the Hong Kong and Macau Affairs Office, said during a press conference that "radical protests... have severely impacted Hong Kong's prosperity and stability, pushing it into a dangerous abyss", Efe news reported.
"I would like to warn all of the criminals: don't ever misjudge the situation and mistake our restraint for weakness," he said in a document issued during the briefing here.
"We would like to make clear to the very small group of unscrupulous and violent criminals and the dirty forces behind them: those who play with fire will perish by it.
"All those people who take the police as their objective or set fire to police stations are creating great harm to society - this has to stop," Yang said.
"We have to pay attention to the extremists who threw the Chinese national flag into the sea, defying national sovereignty and the principle of 'one country, two systems'.
"This has gotten out of hand and we have to bring them to justice."
On Monday, thousands of people joined a general strike in Hong Kong after weeks of unrest in the city.
Yang accused some of the campaigners of believing that "only violence can bring justice".
"They have even forced local residents to participate in their actions. We ask residents to say 'no'. If the protests continue, who do you think will pay the bill?"
Beijing reiterated its support for Hong Kong's leader Carrie Lam.
Yang also defended the Hong Kong police, who have been criticized for their response, and said officers had used "firm methods" to restore order.
More than 12,000 Chinese riot officers arrived in the neighbouring town of Shenzhen to participate in a mock protest dissolution with a view to celebrate the 70th anniversary of the founding of the People's Republic of China, the police announced on the Weibo social network.
( With inputs from IANS )