Observers say sending in troops or taking over the governing of Hong Kong directly is an extreme last resort.
Hong Kong has seen protests all summer. Rally organizers said that a total of roughly 150,000 people attended. A journalist was injured in the eye by tear gas bullets, while another was briefly detained after engaging in an argument with the police over the first journalist's injury, according to local media.
"Losing a bit of money now is not such a problem, (compared) with losing everything that the freedom of Hong Kong used to stand for", Mark Schmidt, 49, a restaurant manager who closed Monday, told Reuters.
Hong Kong has been hit by weeks of sometimes violent protests that began with opposition to a now-suspended extradition law that would have allowed suspects to be tried in mainland courts. "The female protester's clothing was pulled up, exposing her private parts", the human rights group said in a statement.
In recent days, too, Hong Kong police have showed a waning tolerance for the protests and have significantly increased their use of force.
But many in Hong Kong disagree.
Hong Kong witnessed the most widespread and sustained clashes so far with tear gas fired at more than a dozen locations as police, protesters and baton-wielding thugs fought running battles overnight.
Hong Kong is on "the verge of a very risky situation", said Chief Executive Carrie Lam, the Beijing-backed leader who insisted that she has no plans to resign despite the tumult rocking the former British colony.
Mr Yang, however, seemed to downplay any idea of mainland police or military helping with law enforcement, saying the Hong Kong government was "fully capable of punishing the violent crime in accordance with the law, restore order to society, and restore stability to society". He also warned that the city risks a recession as protests continue.
Monday was kicked off by protesters doing all they could to jam up Hong Kong's transit systems and turn morning rush hour into chaos.
Lam's approval ratings have declined to a record low. Just $5 a month. Only 15.1 percent of the participants said they were satisfied with the current administration's performance.
Mr Yang said the government still "firmly supports" both the Hong Kong police force - who have been criticised for their handling of the protests - and Carrie Lam, the city's pro-Beijing leader who protesters want to resign.
Meanwhile, Beijing's agency for managing city affairs, the Hong Kong and Macau Affairs Office, announced that it would hold a press briefing about the protests on Tuesday, following last week's rare press conference. The latest call to action involved a general strike that was held on Monday.
Lam's speech came as a disappointment to many demonstrators, who have been calling for her resignation. Rather than dying down over time, the demonstrations have only grown disruptive.
Experts said Monday's strikes were the biggest to have rocked the city in decades.
Wang Jiangyu, who is an associate law professor at the National University of Singapore, said that while many mainlanders once had sympathy for the protesters' causes, they now view the situation a bit differently.
China promised Hong Kong a high degree of autonomy when it regained sovereignty over the territory from Britain in 1997. The rioting charge has a maximum punishment of 10 years imprisonment.