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 in some of the worst violence in Hong Kong in weeks, with metro stations set ablaze and buildings vandalised, including an outlet of US coffee chain Starbucks.

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, 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 vandalising 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.

Australian Associated Press