* Knifeman attacks several people, bites off politician's ear
* White-masked demonstrators plan Guy Fawkes Day protests
* Xinhua office, other buildings vandalised
* Chinese state media calls for tougher stance on protests
Scores of people were injured in Hong Kong during a chaotic weekend of anti-government protests that left one man in a critical condition, authorities said on Monday, as China called for a tougher stance to end months of unrest.
Riot police stormed several shopping malls packed with families and children on Sunday, following one of the worst days of violence in weeks as police fired tear gas, rubber bullets and a water cannon at crowds of black-clad demonstrators across the Chinese-ruled financial hub on Saturday.
In one bloody incident outside a mall in the eastern suburb of Taikoo Shing on Sunday, a man with a knife slashed several people and bit off part of a politician's ear.
The wounded included a man believed to be the knife-wielder, whom protesters had beaten with sticks. Police said they arrested three men involved, including the suspected 48-year old assailant.
The city's Hospital Authority told Reuters one person was in a critical condition, with two others serious, among a total of 30 injuries from Sunday alone. Local media reported a life-threatening injury was sustained by a male student who fell from a height, but details of the incident remained unclear.
The head of the boy's university called on authorities to investigate the matter in a heated dialogue with students on Monday evening.
Twelve police officers were also injured during weekend clashes, with more than 300 people ranging from 14 to 54 years of age arrested between Friday and Sunday, police said.
While Hong Kong and its many businesses function normally during the week, many protests have sprung up spontaneously at weekends over the past five months.
Pro-democracy protesters are campaigning against what they see as Chinese meddling with the freedoms promised when the former British colony returned to Chinese rule in 1997. China denies doing so, and has blamed Western countries for stirring up trouble.
Chinese state media called on Monday for a tougher line against the protesters who vandalised the local offices of state-run Xinhua news agency and other buildings, saying the violence damaged the city's rule of law.
More demonstrations are planned this week as the protesters keep up pressure for demands that include an independent inquiry into police behaviour and universal suffrage.
"We really see that people are very heavy-hearted. They don't know what is going to happen tonight or maybe the next weekend. And there is a lot of worry," pro-democracy lawmaker Charles Mok told Reuters.
Protesters have circulated plans on social media to mark Guy Fawkes Day on Tuesday by putting on now-banned face masks in areas around Hong Kong.
Many people taking to the streets in recent weeks have worn the white, smiling Guy Fawkes masks made popular by anti-establishment hackers and by the film "V for Vendetta".
The masks have also become common at protests globally, including in Britain and across the United States.
Hong Kong's embattled leader Carrie Lam invoked colonial-era emergency powers last month for the first time in more than 50 years, banning face masks in a move to quell the protests.
Protesters have largely ignored the ruling and worn masks.
The protests have divided Hong Kong and undermined its economy, with the police coming in for particular scrutiny.
Police cancelled a planned press conference on Monday after several journalists from the public broadcaster and other local media turned up wearing helmets with signs that said "investigate police brutality" and "stop police lies", and then refused to leave when asked by officials.
"We are not protesting...We are just using our clothes...to urge the police to change and stop the violence against the journalists," said Ronson Chan of online news site The Stand News. Police said the journalists' actions were "disrespectful" and "deprived the public of access to important information".
Local media associations have condemned what they describe as a heavy-handed approach by the police towards journalists, while officers have said they are responding to an escalating cycle of violence in five months of protests.
Protesters smashed doors and windows and threw petrol bombs at Xinhua's office on Saturday in some of the worst violence in weeks. They also set fire to metro stations and vandalised buildings, including an outlet of U.S. coffee chain Starbucks.
The city's Foreign Correspondents' Club expressed grave concern at the attack on Xinhua, stating that news organisations and journalists must be able to work in Hong Kong free from fear of attack and intimidation.
Mainland businesses, including banks or companies seen as supportive of China's ruling Communist Party, have often been targeted by protesters.
Police said the protests have been a "man-made disaster" for the city with some 45 kilometres (28 miles) of roadside railings dismantled, and 145 rail stations vandalised.
"Rioters' destructive acts serve no other purpose than to vent their anger at grievances real and imagined," said Chief Superintendent Tse Chun-chung on Monday.
"Continuing this rampage is a lose-lose situation for Hong Kong. Everyone is a loser. Please don’t let violence take over our daily life. Everyone deserves freedom from fear."