Chinese President Xi Jinping's surprise meeting with Hong Kong leader Carrie Lam was a 'vote of confidence' in her government's ability to tackle five months of anti-government protests that have rocked the semi-autonomous Chinese territory, a senior official said Tuesday.

Xi met Lam on the sidelines of a trade event in Shanghai on Monday night amid signals from China's central government that it may tighten its grip on Hong Kong to quell the unrest that has at times challenged Chinese rule.

When asked if the meeting reflected Xi's worry about Lam's handling of the unrest, Hong Kong Chief Secretary Matthew Cheung said, 'The reverse is true.'

'The very fact that he is so busy, that he found time to meet, really is a vote of confidence in ourselves' and underlined the importance that Beijing attaches to Hong Kong, Cheung said at a news conference.

Xi 'has a high degree of confidence in the chief executive and also certainly the work of the present government and the political team, so all these are pretty reassuring to us,' he added.

Pro-democracy lawmaker Claudia Mo warned of a tougher stance by Beijing.

'They realized things in Hong Kong have reached a point of no return and there is no choice except for keeping their approval for Carrie Lam with hopes that things will die down,' Mo told The Associated Press. 'The message to Hong Kong people is that we are with her, she has our backing and you better watch out.'

China's official Xinhua News Agency reported that Xi expressed his government's 'high degree of trust' in Lam to stabilize the situation after she briefed him on the crisis.

But Xi also 'demanded unswerving efforts to stop and punish violent activities in accordance with the law' as restoring order was a top priority for Hong Kong, Xinhua said. He also called for more dialogue and efforts to improve people's livelihoods in one of the world's most expensive cities.

China's Communist Party last week indicated it may try to find a way to enact anti-subversion laws in Hong Kong, after such measures were shelved previously due to public opposition.

The protests began in early June against an extradition bill that would have allowed suspects to be sent for trials in mainland China, which many saw as infringing on Hong Kong's judicial freedoms and other rights that were guaranteed when the former British colony return to China in 1997.

Lam abandoned the bill three months into the protests, but the movement by then had grown into calls for greater democracy and police accountability and had become one of Xi's biggest challenges since he came to power in 2012. Lam has invoked emergency powers to ban the use of facial coverings at rallies, provoking further anger.

Hundreds of students defiantly wore masks — including Guy Fawkes masks, which are protest symbols worldwide — in schools Tuesday to mark the one-month anniversary of the ban, local media said. Calls emerged online for protesters to wear Guy Fawkes masks at evening gatherings.

Protests in recent weeks have been marked by violence as hardcore anti-government demonstrators set fires and trashed facilities in clashes with police who used tear gas, and brawls occurred between demonstrators and pro-Chinese activists.

A university student who reportedly fell off an upper floor of a carpark building after police fired tear gas was fighting for his life Tuesday, hospital officials said. Police couldn't immediately provide details.

Television footage showed riot police firing tear gas at the building early Monday after objects were hurled down at the street at them when they chased off a mob. Minutes later, medical workers found the youth sprawled in a pool of blood on the second floor of the building. He was believed to have plunged from the third floor, local media said.

More than 3,300 people have been arrested since the protests started. In one bloody incident Sunday night, a knife-wielding man believed to be a Beijing supporter slashed two people after an argument and bit off part of a politician's ear outside a mall. Police have arrested the assailant and two men who attacked him.

Cheung said the government plans to hold a second community dialogue after Nov. 24 district elections. Lam held her first town hall meeting on Sept. 26, where she was criticized by angry residents.