Hong Kong police have arrested a Form Six pupil for posting online messages in an alleged attempt to get people to boycott more than 100 businesses that advertised with free-to-air broadcaster TVB.

Without naming the station, police said on Thursday the 18-year-old male suspect was found to have posted messages on a Facebook group since May last year and encouraged others to blacklist advertisers to try to cause reputational and financial losses to a broadcaster.

A force insider said the teenager – who was the Facebook group’s administrator – had invited internet users to post “angry face” emojis on the site and boycott firms that had placed adverts with Television Broadcasts, a frequent target of anti-government protesters during the city’s social unrest in 2019.

Radicals accused TVB of having a pro-police bias and targeted its journalists and equipment.

The student was arrested by police’s cyber security and technology crime bureau in Sham Shui Po on Wednesday.

Superintendent Wilson Tam.

The bureau’s Superintendent Wilson Tam Wai-shun did not divulge evidence of the alleged criminal intimidation in the messages but said the suspect was using threatening ways to try to pressure firms into pulling their adverts in his 2,000 posts targeting more than 100 entities.

“We are not looking into one or two posts or one or two wordings to see if there are criminally intimidating elements, but more than 2,000 postings over a long period as a whole,” he said.

Asked whether any other campaigns calling for business boycotts might also constitute criminal intimidation, Tam said police would need to look at them on a case-by-case basis.

The student also allegedly encouraged others to take part in unlawful protests through the online platform. According to the source, the teen posted a message on another Facebook page calling on others to join an illegal assembly in September 2019.

He was detained for conspiracy to commit criminal intimidation and inciting others to take part in the unlawful assembly.

Police have not ruled out more arrests.

Separately, a 26-year-old man was arrested in Ma On Shan for posting messages on a popular online forum urging others to attack TVB staff, and a police officer’s infant daughter. The police source said the suspect used the LIHKG platform in November 2019 and May last year to incite others to attack staff of TVB’s news department.

“The suspect claimed in the online posts that the broadcaster reported fake news,” he said.

He was also arrested for contempt of court after allegedly posting photos of a policeman and the officer’s infant daughter while inciting others to attack her.

A court injunction, issued in 2019 and still in force, bans the doxxing of police officers.

Tam said the man was detained for inciting others to wound with intent and inciting others to assault occasioning actual bodily harm.

Police picked up three mobile phones, two tablets and three computers during the two operations. As of Thursday evening, both suspects were still being detained for inquiries. Tam said the operations were continuing and further arrests were possible.

In a statement, TVB denounced illegal acts committed online and offline and expressed gratitude for the police investigation and moves to bring offenders to justice.