SHANGHAI (AFP) -- Chinese President Xi Jinping has expressed a "high degree of trust" in Hong Kong's unpopular leader Carrie Lam as the two met after months of increasingly violent protests in the semi-autonomous city.

Xi's show of support follows speculation that Beijing was preparing to remove Lam as city authorities struggle to contain pro-democracy demonstrations that have rocked the financial hub.

Their meeting on the sidelines of an international trade fair Monday followed another weekend of violence in Hong Kong that was marked by a knife attack and the vandalising of an office of China's official Xinhua news agency.

Xi said Lam has "done a lot of hard work" and strived to stabilise the situation in Hong Kong, according to a Xinhua readout of their meeting.

"Xi voiced the central government's high degree of trust in Lam and full acknowledgement of the work of her and her governance team," the state news agency said.

"Ending violence and chaos and restoring order remain the most important task for Hong Kong at present," Xi said.

Xi also called for "effective efforts" to be made in improving people's lives and having dialogue with all sectors of society.

Unscheduled Beijing talks

China has run the city under a special "one country, two systems" model, which allows Hong Kong liberties not seen on the mainland, since its handover from the British in 1997.

But public anger has been building for years over fears that Beijing has begun eroding those freedoms, especially since Xi came to power.

Protesters have issued a list of demands, including universal suffrage and an investigation into abuses by police.

The Chinese Communist Party agreed at a leadership meeting last week to "improve" the way Hong Kong's chief executive and key officials are appointed and removed, but it provided no other details.

The party also warned it would "never tolerate" any challenge to "one country, two systems".

Lam was originally supposed to return to Hong Kong after attending the second China International Import Expo in Shanghai, but on Sunday her office said she would meet with Chinese government officials in Beijing on Wednesday.

Willy Lam, an expert on Chinese politics, said the meeting will be publicly billed as discussing the protests and Hong Kong's involvement in China's huge Greater Bay Area economic zone.

"But I think the real reason has to do with whether they might discuss a replacement for Carrie Lam," he told AFP.

"Her performance has proven to be near disastrous and she has lost the confidence of Beijing." (AFP)