Armed police and security guards yesterday shut down a screening about the murder of political commentator Kem Ley and arrested four young activists in charge of the event.

The Khmer Student Intelligent League Association (KSILA) – some of them former students of Ley’s – had arranged to screen a two-month-old Al Jazeera report, with Khmer subtitles, about the suspicious circumstances surrounding Ley’s murder for a small audience of 20 in a private residence.

But a force of almost 50 men surrounded the venue and interrogated the young organisers in heated tones, saying they had not asked permission to show the film.

Four activists – Moung Sony, Heng Samnang, Soung Neakpon and Vorn Chanlut – were then asked to board a police vehicle and were transported to Tuol Sangke police station, where they were questioned for more than three hours.

They were released shortly before 6pm after thumb-printing a contract saying they would ask permission from municipal authorities before screening the video or face the legal consequences.

The 25-minute video, titled Cambodia’s Deadly Politics, argues that Oeut Ang, the former soldier charged with killing Ley, met with district and military officials a week before the murder.

Critics and observers have long suggested Ang was a fall man for the government; Ley was gunned down just days after he commented on a damning report from Global Witness, which highlighted a nexus of illicit business connections to Prime Minister Hun Sen’s family.

Prior to his arrest, Moung Sony defended the plan to show the film. “There’s no law that says I have to ask permission; I am just screening at home,” he said.

But Russey Keo Deputy Governor Prach Seyha was quick to dismiss that assertion.

“Your action is involved with political incitement . . . Kem Ley’s case is under the jurisdiction of the court . . . Another thing is that the location was not yet approved by the authorities,” he said.

KSILA general secretary Chek Chetra said the authorities’ heavy-handed response was a form of intimidation.

“We are really disappointed about this ban, because the authorities have used their power to violate our right to gather and act,” he said.

“We have not done anything to affect them, so it is a serious rights violation.”

Armed police and security guards gather to shut down the screening of the news report on Kem Ley’s murder yesterday in Phnom Penh. Pha Lina

Government spokesman Phay Siphan was quick to defend the show of force by authorities yesterday, arguing in a Facebook post that screening the video – in which he is interviewed – would discredit the court’s investigation of Ang.

He accused the group, which he described as an “illegal organisation”, of politically benefitting from the death of Ley.

“Another doubt is why they respect Kem Ley’s body as the legend of Cambodia . . . he is just a commentator,” wrote Siphan, who has attempted to downplay Ley’s popularity in other posts.

He described the activists’ screening of an exaggerated foreign news report as “a clear act of incitement, because the information does not reflect the complete truth” and said the ban prevented “rumour [from] influencing national security”.

Reached by phone yesterday, Siphan added the video would be used as proof there was someone “behind the killer”, but “we caught the killer already”, he claimed.

“We are not scared [of the report], but we have to carry out the law,” he said.

However, Siphan said the government would take no steps to block CCTV footage of the killing and its aftermath – published on Fresh News and circulated on social media which was used as evidence in the court room.

After his release yesterday evening, young activist Heng Samnang said Siphan was entitled to his opinion, but he and his fellow young activists were simply seeking the truth.

“We just want people to know about the murder of Kem Ley,” he said.

It’s not the first time authorities have sought to block screenings of films that cast them in a negative light. Last April, the Ministry of Culture and Fine Arts banned a screening of a documentary film about murdered environmentalist Chut Wutty.

The government also banned the film Who Killed Chea Vichea? about the assassination of the influential union leader.

Both murders, like Ley’s, have been haunted by the spectre of government involvement.