The Hong Kong demonstrations began almost three months ago as a protest against a new extradition law.

Wang Ying has for the last four years identified herself as a diehard fan of Chinese boy band star Lay Zhang. Recently, the 17-year-old also started describing herself as a patriot who supports China's stance on Hong Kong.

The high school student from Shanghai is among the Chinese citizens who in recent weeks have flocked to Western social media platforms such as Instagram and Twitter to criticise demonstrators in the former British colony.

She is part of a growing offensive emerging from China in recent days aimed at promoting Beijing's narrative about what is happening in Hong Kong to an overseas audience. State media outlets, Chinese celebrities and regular internet users have all banded together behind the effort.

While little news or video footage of the Hong Kong protests made its way into mainland China in the early weeks, the subject now dominates the news and most-read topic lists on China's Twitter-like Weibo, with calls for Chinese citizens to take action to "protect Hong Kong".

China's government-owned media outlets have flooded Internet platforms both inside and outside the country with stories and images portraying the Hong Kong protests as the work of "terrorists" manipulated by Western powers and "radical forces".

They have paid to promote their coverage of Hong Kong on sites including Twitter and Facebook, which are banned on the mainland. The companies said Tuesday that the Chinese government has also mounted a propaganda campaign using fake accounts, thousands of which were taken down in recent days.

The efforts have unleashed an unusual dynamic in which mainland citizens who are normally subject to strict controls on their online behaviour have been using virtual private networks to bypass the "Great Firewall" and spread anti-protest messages internationally, as well as on Chinese social media sites.

"It's only really the hypernationalists that are given free rein, their content isn't censored," said Fergus Ryan, an analyst at the Australian Strategic Policy Institute (ASPI) who studies Chinese social media. "They're allowed to conduct campaigns, they're able to organise online ... so that happens in China within the Great Firewall, and then we see also it spill out into the wider Internet," he said.

But analysts say it's unclear who Beijing is targeting with the campaign, or what the impact has been.

Lee Foster, an intelligence analyst at U.S. cybersecurity firm FireEye, said the fake account campaigns on Twitter and Facebook were "relatively unsophisticated".

"(It's) not too dissimilar we've seen from Russia about 4-5 years ago in terms of very simplistic personas and the use of identical messaging across accounts," he said.

King-wa Fu, an associate professor at the University of Hong Kong's Journalism and Media Centre, said he suspected the impact within Hong Kong was minimal.

"The majority of Hong Kong consume local media content," he said.

"Fan girls" and celebrities

The Hong Kong demonstrations began almost three months ago as a protest against a new extradition law and have since snowballed into a broader movement to defend the city-state's civil liberties in the face of what is perceived to be tightening mainland control.

Wang said she and her group of online peers, also known as 'fan girls' or 'fanquan girls', began to campaign against the protests after her idol Zhang, a member of South Korean boy band Exo, joined other Chinese celebrities last week to say that he backed the Hong Kong police and Beijing's territorial sovereignty.

"Since our big brother loves our country so much, we fans have to support him," she told Reuters. "So I went on Instagram to post messages such as 'Hong Kong is part of China,' 'Reject violence,' and 'Hong Kong police are the best!'"

They were joined by other internet denizens such as those on 'Di Bar,' a discussion forum that is part of search engine giant Baidu's platform, where calls went out to the group's 31.3 million members asking them to flood overseas social media platforms with similar slogans and posts.

The internet movements were endorsed by Chinese state broadcaster CCTV on Sunday on its nightly news programme, one of China's most-watched shows.

"These days, from fanquan girls to Di Bar, netizens to overseas students, all the forces which love Hong Kong and China have united to support and safeguard the city,' said newscaster Gang Qiang.

State television's English-language channel CGTN, the official Xinhua news agency and the Communist Party's People's Daily have all taken to Twitter and Facebook with gusto, denouncing the protesters and putting out Beijing's voice.

"What must be hidden and has to flee is not good, but evil," CGTN said in a tweet on Wednesday that was accompanied by a video of masked protesters with captions saying they wanted to hide their identities to avoid retribution.

Xinhua and CGTN paid to promote their Hong Kong coverage, according to Twitter's Ads Transparency Center. Neither outlet responded to requests for comment.

Twitter told Reuters on Monday it would no longer accept advertising from state-controlled news media.

China denounced the moves by Twitter and Facebook on Tuesday, saying it had a right to put out its own views. China's foreign ministry on Tuesday also sent a letter accompanied by a 42-page document to foreign media outlets including Reuters, Bloomberg and the Wall Street Journal outlining Beijing's stance on the events in Hong Kong.

The documents included a timeline of how the protests began, saying that Hong Kong's opposition and some "radical forces" had used the pretext of peaceful demonstration to engage in violent protests, as well as articles which it said pointed to links between "foreign forces" and protesters.