Beijing said the Hong Kong government and police are "fully capable" of punishing what he called "criminal activities" and restore public order, a spokesperson for China's Hong Kong Macau Affairs Office said at a press conference on Tuesday.
The spokesman added that the People's Liberation Army is "under the leadership, the command of the Communist party of China" and it "acts in the accordance with law." He added that the city's authorities can take it upon themselves to punish violators of the law with the "strong support" from the Chinese central government, and the backing of the people from the mainland and Hong Kong.
His comments come amid continued violence in Hong Kong. On Monday evening, violent clashes between the city's police force and protesters broke out during another demonstration in the North Point district. A group of men armed with sticks tried to attack black-clad protesters, according to a Reuters report. The police in response used tear gas on the crowd.
Hong Kong has been rocked by political unrest for nearly three months now. Hundreds of thousands of protesters have taken to the streets since early June, spurred by their opposition to a proposed bill that would have allowed people in Hong Kong to be extradited to Mainland China. The proposal has been suspended — but not fully withdrawn — yet demonstrations continue and have shifted into a movement calling for autonomy, full democracy and the ousting of the city's leader Carrie Lam.
It is unlikely that Beijing will deploy troops to Hong Kong before China's 70th anniversary on October 1, said Willy Lam, adjunct professor at Chinese University of Hong Kong.
He said a possible outcome could be that mainland law enforcers based in Shenzhen join the Hong Kong police "to put down the unrest and restore law and order." In fact, the professor said that might have already happened, but there is no hard and fast evidence.
At the press conference on Tuesday, the Beijing spokesperson condemned the violence and insisted that the protesters should be held accountable.
He said, "don't ever misjudge the situation and mistake our restraint for weakness."
"Don't ever estimate the firm resolve and immense strength of the central government," said Yang Guang, spokesman for the Hong Kong Affairs Office.
Beijing authorities described the protesters' actions as "extreme and criminal acts of violence," and a "serious violation of public order."
That's a potential signal that the mainland government can deploy the PLA if deemed necessary, after the city's leader Lam dismissed "untrue" rumors that troops will be deployed into the city's streets to help control protesters.
The Hong Kong Police told the press that it arrested 148 protesters on Monday. A spokesperson said that the demonstrators have gone too far as they have now "destroyed the rule of law" and "hampered public safety."
"They show a total disregard of the rule of law. Many citizens were living in fear as they worry such violence will happen to them," he said at the Tuesday presser.
The pro-democracy demonstrations started out peaceful but have taken a violent turn in recent weeks. Violence has erupted between the police and protesters, protesters with differing opinions and suspected triad gang members.
In a video that went viral on Twitter on Monday evening, a man driving through North Point got out of his car, only to get punched in the face and his car smashed by protesters for no apparent reason.
— CNBC's Grace Shao and Reuters contributed to this report.