Chinese state media has urged authorities to take a “tougher line” against protesters in Hong Kong who vandalised state-run Xinhua news agency and other buildings at the weekend, saying the violence damaged the city’s rule of law.

The call on Monday comes as the city braces for more protests following a violent incident on Sunday, in which two people were left in critical condition.

In an editorial, state-backed China Daily newspaper criticised the “wanton” attacks by “naive” demonstrators, adding, “They are doomed to fail simply because their violence will encounter the full weight of the law.”

Police fired tear gas at black-clad protesters on Saturday and Sunday in some of the worst violence in the Asian financial hub in weeks, with metro stations set ablaze and buildings vandalised.

Violence also erupted on Sunday after a man with a knife attacked several people and bit off part of the ear of a pro-democracy politician. Two of the victims are reportedly in critical condition, according to reports.

The past five months of anti-government protests in the former British colony represent the biggest popular challenge to President Xi Jinping’s government since he took over China’s leadership in late 2012.

Protesters are angry at China’s perceived meddling with Hong Kong’s freedoms, including its legal system, since the Asian financial hub returned to Chinese rule in 1997. China denies the accusation.

The widely-read Global Times tabloid on Sunday condemned the protesters’ actions targeting Xinhua and called for action by Hong Kong’s enforcement agencies.

“Due to the symbolic image of Xinhua, the vandalizing of its branch is not only a provocation to the rule of law in Hong Kong, but also to the central government and the Chinese mainland, which is the rioters’ main purpose,” it said.

On Friday, after a meeting of China’s top leadership, a senior Chinese official said it would not tolerate separatism or threats to national security in Hong Kong and would “perfect” the way it appointed the city’s leader.