Chinese state-run media on Monday called for a "tougher line" on democracy protesters in Hong Kong as it denounced a "terroristic" attack on a state news agency during another weekend of violence in the semi-autonomous city.

"Vandalizing a news agency is as terroristic as challenging the bottom line of civilization," Communist Party mouthpiece People's Daily said in a Facebook post.

The post was accompanied by a video of a man being beaten and stripped of his clothing by people the publication called "rioters" in the Mong Kok area.

Photo: AFP / VIVEK PRAKASH

"Intensifying violence in Hong Kong calls for tougher line to restore order," the state-run China Daily, an English-language mainland newspaper, said in the headline of an editorial.

The protesters "court the indulgence extended to them by friendly local and Western media outlets, while seeking to silence those trying to put the protests in the spotlight of truth," the article said.

Photo: AFP / VIVEK PRAKASH

"They are doomed to fail simply because their violence will encounter the full weight of the law."

China has run Hong Kong under a special "one country, two systems" model, which allows the city liberties not seen on the mainland, since the financial hub's 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 President Xi Jinping came to power.

Photo: AFP / Anthony WALLACE

Months of unrest

The nationalist tabloid Global Times called in an editorial on Sunday for "Hong Kong's law enforcement agencies to bring the mob to justice as soon as possible" for vandalising Xinhua's office.

Neither the editorials nor People's Daily's Facebook post mentioned a knife attack on Sunday in Tai Koo Shing, a middle-class neighbourhood on Hong Kong's main island where a rally had been taking place, which left at least five people wounded.

Eyewitnesses told local media that a Mandarin-speaking man attacked people on Sunday shortly after shouting pro-Beijing slogans. In Hong Kong, the lingua franca is Cantonese.

Live footage showed Andrew Chiu, a local pro-democracy councillor, having his ear bitten off after trying to subdue the attacker, while a second man was seen unconscious in a growing pool of blood as bystanders desperately tried to stem wounds to his back.

Hong Kong has seen months of protests, initially sparked by opposition to a now-scrapped proposal to allow extraditions of criminal suspects to mainland China.

They quickly snowballed into a wider anti-government movement after Beijing and local leaders in Hong Kong took a hard line.

Beijing warned on Friday after a four-day meeting of Communist Party leaders that it would not tolerate any challenges to its authority over Hong Kong, while laying out plans to boost patriotism in the city and change how its leader is chosen or removed.

China Daily also noted that the party plans to strengthen Hong Kong's legal system to "safeguard national security".

"Those Hong Kong residents whose lives have been disrupted by the intensifying violence of intimidation -- instigated and organized by those hoping to use Hong Kong as a means to destabilize the nation -- will be glad when life returns to normal," the newspaper said.