ONE by one, they began disappearing.

Five men linked to a Hong Kong publishing house have vanished since October, sending chills through the former British colony as anxiety grew that Chinese control over the city was tightening.

At first it was only speculation. The mainland government was the obvious suspect in the disappearances, but little could be proved.

The Chinese Communist Party said nothing.

But that silence has been shattered by a leaked document reported to come from inside the party that describes a plan to “exterminate” dissenting materials and those responsible for disseminating them.

According to an article published by The Sunday Times, the leaked document is called the Guangdong Action Plan and aims to “wipe out at the source” illegal and pornographic publications.

By drawing on a central government order dated April 25, 2015, the initiative appears to grant authorisation for cross-border operations to stamp out the publication of materials that are banned in the mainland. The document singles out Hong Kong and Taiwan as the prime targets.

FIVE DISAPPEAR FROM PUBLISHING COMPANY

Swedish citizen of Chinese birth, Gui Minhai, was the first to go when he vanished from a Thai resort in October. Soon after four of his colleagues, including Lee Bo who holds a British passport, also disappeared. The disappearances have been shrouded in mysterious and inexplicable circumstances. None of them have been seen in public since.

All five men are either stakeholders or employees at a Hong Kong publisher Mighty Current. Many of the books published by the company contain scandalous gossip about China’s elite, including top members of the Chinese Communist Party.

At the time they began vanishing, the publisher was planning to release a book about a former girlfriend of Chinese president Xi Jinping.

Such books are illegal in China but have proved immensely popular among mainland tourists.

Guangdong is the province bordering Hong Kong and the so-called action plan encourages a “counter-attack” against the materials, The Sunday Times reported.

“Intensify the external composite counter-attack on banned books,” the document said.

LEAKED CHINESE REPORT

The leaked report has given credence to democratic advocates in Hong Kong who have long claimed mainland politicians were responsible for the abductions.

There has been speculation in the past of China interfering with the politics of Hong Kong, but it is the first time residents are believed to have been abducted from the territory by mainland agents.

However such actions are in direct contravention of the political agreement signed by the Communist Party when Britain handed the territory back to Chinese rule in 1997.

Under the agreement of “one country, two systems” Hong Kong maintains its own legal, political and economic apparatuses.

The scandal has caused widespread concern among those in the autonomous Chinese territory about the real level of freedom Hong Kong enjoys under Chinese rule.

DOUBTS OVER CHINESE INVOLVEMENT

However some have cast doubt over the veracity of the reported action plan, saying it would be impossible to truly implement and IT breaks Hong Kong law.

Speaking to the South China Morning Post, a member of the Legislative Council of Hong Kong, Ip Kwok-him, said: “I think such a report is not very trustworthy ... because the freedom of publication is protected under the law, which means you can publish or sell these books in Hong Kong.”

However he added that “Beijing had repeatedly said it would not allow Hong Kong to become a base for subversion”.

The belief that China is responsible has sparked fury among politicians and activists in Hong Kong, adding to growing unease freedoms in the city are being eroded.

For them, the reports of the leaked plan also help to explain a well-documented pattern of abductions and disappearances of dissidents from Thailand, Laos, Cambodia and Myanmar.

China, they say, is clamping down.