Activists who have advocated independence for Hong Kong say they have been harassed or followed by pro-China local newspapers in recent months, while Beijing has stepped up its rhetoric against what it calls the "dangerous absurdity" of independence.
Beijing's refusal to grant full democracy to Hong Kong, which mostly runs its own affairs under a one-country, two-systems arrangement since the former British colony returned to China in 1997, prompted three months of street protests in 2014 and growing calls for independence for the city.
In a July poll by the Chinese University of Hong Kong, 17 percent of the roughly 1,000 respondents said they supported independence, but Chinese state media call such views "poisonous".
Six candidates in next month's legislative elections have been excluded from the ballot by Hong Kong's Electoral Affairs Commission for pro-independence opinions, which it says are incompatible with the city's governance laws.
One of the six, Edward Leung, spokesman for Hong Kong Indigenous, a localist party set up in 2015, and his colleague Ray Wong say they were tailed for a month this summer by men claiming to be from a newspaper with Beijing links.
And this month Leung was filmed in a scuffle with a reporter from a local pro-China paper, Ta Kung Pao, which published front-page pictures of the tussle along with a story claiming to have exposed his hidden wealth.
Leung, who suffered grazes on his face and neck from the incident, said the reporter and another man approached him earlier that evening with details on his private life while trying to film his reaction. The scuffle occurred later when Leung confronted the reporter, who also turned up at the underground station nearest to the apartment the article said was his home.
TKP's article said Leung had started the fight, and its reporter, surnamed Lo, had sustained similar injuries.
Leung said the man accompanying Lo that evening had also been one of two men who had followed him and Wong in a black car for a month.
In a video filmed on Aug. 7 by Leung and posted online by him, Wong confronts the men in the car and asks where they are from.
The driver is heard to say: "You know where I'm from. It's 'grandpa'," using a popular term to describe China's government. The driver added that he was from a newspaper, but didn't identify the title.
"The Chinese Communist Party is making use of Hong Kong's Ta Kung Pao, their minion, to gather intelligence on us," Wong told Reuters.
Ta Kung Pao did not respond to requests for comment.
China's State Council Information Office and the mainland's representative in Hong Kong, the Liaison Office, did not return requests for comment.
Three employees at Ta Kung Pao, which they said had an editorial staff of about 100, told Reuters they didn't recognise Lo or the other two men.
"We think it's very strange. They're not our reporters," said one, who declined to be named.
Wong said his family had also been approached earlier this year by three men claiming to work for a Chinese government entity that he declined to name.
"They told my family, 'Be careful, your son may end up like Lee Bo,'" Wong said, referring to a bookseller who went missing in Hong Kong in late December and showed up months later under police custody in mainland China.
A third activist, Andy Chan Ho-tin, who founded the Hong Kong National Party to promote Hong Kong independence, said he must also have been followed in April by reporters at another pro-Beijing newspaper, Wen Wei Po.
He was not aware of it until the paper printed an article and pictures alleging Chan's links to another activist charged with arson.
The article said it had continuously staked Chan out at the party's office and various university campus forums.
Wen Wei Po declined to comment.
Professor Sonny Lo, co-director of the Education University of Hong Kong's Centre for Greater China Studies and the Centre for Governance and Citizenship, said traditional leftist newspapers had undergone a "strategic transformation" in recent years, adding investigative teams partly to intimidate and gather intelligence on perceived threats in the protest movements.
"We're seeing a far more sophisticated and coordinated strategy at work now from these newspapers in isolating and attacking targets," said Lo, who has researched China's underground influence in Hong Kong.