Riot police fanned out across Hong Kong on Monday night as groups of pro-democracy protesters took to the streets in continued violence since the government banned face masks at rallies.

The scenes in at least six locations across the special administrative region of China have almost become the norm, with groups of black-clad youths setting up road barriers to block traffic, smashing traffic lights and shops linked to China, and breaking into and vandalizing shuttered subway stations.

Riot police fired tear gas, charged at crowds and took position on streets. A number of protesters were detained. The night’s violence broke the day’s relative calm, when hundreds of people gathered in several malls to sing protest songs and chant slogans.

The mask ban, which took effect Saturday under an emergency law, has led to more anger, instead of deterring the anti-government demonstrations that have rocked the international financial hub for four months.

“Wearing a mask is not a crime!” has become a new battle cry at daily rallies that have degenerated into skirmishes between police and protesters.

Riot police officers detain a man during an anti-government protest in front of a police station in Mong Kok district on Monday. (Jorge Silva/Reuters)

Earlier Monday, two protesters were charged with violating Hong Kong’s new ban on wearing masks at rallies, a move likely to add to a backlash that has thrown the semi-autonomous region into deeper crisis.

An 18-year-old student and a 38-year-old unemployed woman were the first to be prosecuted under the ban, which came into force Saturday under sweeping emergency powers aimed at quashing violence in the protests for more democratic freedoms.

Detained early Saturday shortly after the ban took effect, the two were also charged with taking part in unlawful assembly, which carries a heavier penalty of up to five years in jail. A conviction under the mask ban is punishable by up to a year in prison and a fine. They were both released on bail pending trial.

“I am wearing a mask to come here today … this is a form of silent protest,” said 16-year-old student Bao Yeung, who was among a large group of supporters outside the court.

Subway stations closed

The protests were sparked by a proposed law that would have allowed some criminal suspects to be sent to mainland China for trial, but have since morphed into a larger anti-government movement. Protesters are upset at what they say are Beijing’s increasing influence over the former British colony, which was promised a level of autonomy when it was handed back to Chinese rule in 1997.

Sunday’s protests drew a first warning from the Chinese military after protesters pointed lasers at one of its barracks in Hong Kong. Police said protesters also attacked bystanders, including two men left unconscious after bloody beatings and a woman who took photos of the violence.

In a statement Monday, police said the “public order of the whole city is being pushed to the verge of a very dangerous situation.” The chaos has led many shops and public services to shutter and panic buying in some areas.

The city’s MTR network of subways and trains was entirely closed Saturday and partially reopened Sunday but was quickly targeted again by protesters. Most stations remained closed Monday amid fears of more protests.

Hong Kong’s High Court has rejected a second effort to invalidate the mask ban but agreed to hear later this month an application by 24 legislators against Hong Kong leader Carrie Lam’s use of the colonial-era Emergency Regulations Ordinance to impose the ban without legislative approval.

Lam has said that the mask ban will make the identification of rioters easier for police and that other measures are possible if violence continues.

Pro-democracy protesters set up barricade at a demonstration in Wan Chai district on Sunday in Hong Kong after the government invoked emergency powers on Friday to introduce an anti-mask law. (Anthony Kwan/Getty Images)

Critics fear Lam’s use of the emergency law that gives her broad powers to implement any measures she deems necessary could pave the way for more draconian moves. The law was enacted by the British in 1922 to quell a seamen’s strike and was last used in 1967 to crush riots.

Lam has said she will seek the legislature’s backing for the mask ban when it meets next on Oct. 16.

Enforcement of the ban is tricky in a city where many have worn surgical masks since a deadly respiratory disease outbreak in 2003.

Two teens have been injured by gunfire from officers under attack this week. An 18-year-old protester, shot at close range by a riot officer on Oct. 1, was charged with rioting and assaulting police. A 14-year-old teen, who suffered a gunshot wound to his thigh Friday night, was arrested.