BEIJING - China on Tuesday (July 2) condemned “extremists” who stormed Hong Kong’s Parliament building, calling their act a “blatant challenge to the one-country-two-systems” model that governs the city.

In its strongest response yet, the central government issued a statement expressing “resolute support” for the Hong Kong government and the police for handling Monday night’s dramatic protest, and their criminal investigation of the demonstrators.

A spokesman for the Hong Kong and Macau Affairs Office said July 1 was meant to be a celebratory day to commemorate the return of Hong Kong to China.

“Yet, some extremists on the pretext of opposing the amendments to the relevant Bill of the special administration region government, attacked the Legislative Council building in an extremely violent manner and deliberately damaged its facilities,” said the statement.

“This serious illegal act tramples on the rule of law in Hong Kong, undermines Hong Kong's social order and undermines the fundamental interests of Hong Kong. It is a blatant challenge to the ‘one country, two systems’ bottom line.”

Beijing has so far been restrained in its response to the mass protests in Hong Kong over a controversial extradition Bill proposed by Chief Executive Carrie Lam’s administration.

Opponents saw it as yet another attempt by China to tighten its grip on the city and control dissent as the law would potentially allow Beijing to grab suspects in Hong Kong to face the law on the mainland.

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More than a million people have taken to the streets to oppose the law, which has forced Mrs Lam to apologise and suspend it.

On Monday night, things took an ugly turn when hundreds of protesters in helmets and masks barged into and took over the Legislative Council building. The police returned at midnight and reclaimed the premises after firing tear gas to disperse the crowd.

China had earlier blamed “foreign forces” for the mass street protests. On Monday, it also hit out at Hong Kong’s former colonial ruler Britain after its foreign secretary spoke up for the city’s freedoms.

While Chinese censors have been scrubbing mention and images of the protests on the mainland for weeks now, state media let loose after the turn of events on Monday night, producing strongly-worded editorials condemning the violence.

State-run TV news channels also reported Mrs Lam’s 4am press conference in which she vowed to take action.

Nationalistic tabloid Global Times called for “zero tolerance” in an editorial on Tuesday, saying it was “the only remedy for such destructive behaviour”.

“Out of blind arrogance and rage, protesters showed a complete disregard for law and order,” said the editorial.

Chinese netizens responding to the news reports have called for tough justice.

“Investigate the violations to the end, never tolerate!” said one on Chinese blogging site, Weibo.

“It is a group of low-level types taking the opportunity to make trouble. This large-scale protest has devolved into a riot. These people don't care, they just want to take the opportunity to vent, or even rob,” said another.

But some questioned the "one country, two systems" policy.

One netizen said: "There's definitely a problem with the policies towards Taiwan and Hong Kong. Why does the central government think that as long as it gives enough benefits and special rights, the people will be loyal to you?"

Said another netizen: "One country, two systems is too lax, and this is the result. If Hong Kong wants to return to normal, it should start with decolonisation and change the name of Victoria Harbour to Oriental Pearl Harbour."