The article was published on Wednesday on the front page of Study Times, a newspaper published three times a week and affiliated with the Central Party School, the party’s top academy.

Cabinet members follow Hong Kong leader and apologise

With the internet transmitting and magnifying threats, Chen said the country needed to strengthen law enforcement’s online propaganda apparatus and regulations to guard against “ideological risks”.

“[We must] resolutely strike down political rumours and harmful information on the internet,” he wrote. “[We should] innovate and improve our work in guiding public opinion, and strictly prevent ‘black swan’ or ‘grey rhino’ public opinion risks.”

While the 4,000-word article did not refer directly to the protests in Hong Kong over the extradition bill in the last two weeks, it underlined Beijing’s long-held position to stop the city’s civil society having an impact on the mainland, analysts said.

Beijing-based political scientist Wu Qiang said the central government had “always been wary of civil movements in Hong Kong spreading to the mainland” and it was a coincidence that the article appeared so soon after the demonstrations.

“I believe the piece was timed for the sensitive month of June [in general],” Wu said.

June was a particularly sensitive time this year, with June 4 marking the 30th anniversary of the bloody Tiananmen crackdown on pro-democracy protests in Beijing, a taboo subject on the mainland.

As Chinese abroad, including those in Hong Kong, remembered the protesters killed in the violence three decades ago, the central government ensured dead silence in public discussion on the subject on the mainland.

Censorship of the protests in Hong Kong in the past two weeks against the extradition bill has been similarly tight. Most discussion about the protests was either blocked by China’s “Great Firewall” or deleted on domestic social media, with some accounts scrubbed entirely for mentioning them.

Chinese media have also remained largely silent on the demonstrations except for some state-run outlets denouncing the protests as incited by “foreign forces”.

Beihang University law professor Tian Feilong said that while the Study Times article was largely set against the rising confrontation with the United States, the Hong Kong protests would only confirm Beijing’s fears.

“The extradition law has underlined a much deeper problem in ‘one country, two systems’,” Tian said. “There’s a profound distrust of the values and the political systems from both sides.”

Chen started his article by referring to a speech by President Xi Jinping in January laying out a long list of risks and uncertainties, ranging from financial threats to social stability issues that he said could jeopardise the rule of the party.

Chen went on to warn against a few types of “hostile forces” – such as separatism, terrorism and “evil cults” – and described how to tackle them.

“Enemies of all sorts are converging: hostile forces collude with separatist forces, those from inside collude with those from outside, and the old guard collude with the new generation,” he wrote.

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Chen called for a prolonged battle against the threat of a “colour revolution”, adding that it should be nipped at the bud.

Chen is widely seen as a rising star in Chinese politics, having worked with Xi in Zhejiang province in the early and mid-2000s.

In 2015, he was promoted to deputy secretary general of the Leading Small Group for the Comprehensive Deepening of Reform, a party organ founded and chaired by Xi since 2013.

In 2016, Chen was sent to govern Wuhan in central China to broaden his experience, before being appointed last year to oversee China’s law enforcement.