Hun Sen has vowed to hunt down a hacker who defaced the prime minister’s personal website on Saturday with images of government security forces beating protesters.

A video prefaced by a logo for the international “hacktivist” collective Anonymous and uploaded to YouTube by the user “Khmer Troop” showcases the defaced website with audio in Khmer threatening more damaging attacks unless Hun Sen stops “hurting people”.

The clip shows the site – which was launched last year – stacked with more than a dozen pictures, topped with a photo of the premier wearing a superimposed crown captioned “the emperor of Facebook”.

Underneath, photos show scenes of brutality, some at the hands of government security forces. The images depict the crackdown on striking workers in 2014 in Phnom Penh – where five people were shot dead – an attack on two opposition lawmakers carried out by members of the premier’s personal Bodyguard Unit, and the aftermath of the 1997 grenade attack against Sam Rainsy’s Khmer Front Party.

“This is just the so-called introduction or advice for Samdech; this is the first step, the first blow,” says the artificially altered voice, before threatening to release damaging information that would “impact upon the premier’s popularity greatly”.

“Samdech uses power just as he wants to by hurting other people . . . all these issues make people angry . . . if Samdech continues to cause problems, I will release it, I will make my second blow or slap to make Samdech wake up and be embarrassed . . . but if Samdech can turn over a new leaf . . . and stop causing problems, I will not release it.”

A message on Hun Sen’s Facebook page posted immediately following the attack linked the “cyber crime” to the opposition party, which “always looked for dishonest ways to attack [Hun Sen]”.

“No matter where the perpetrators come from, they must take responsibility before national and international law,” it said.

“The government’s experts on combating Information Technology (IT) crimes are investigating the source of the hackers in order to bring them for prosecution.”

Cambodia National Rescue Party spokesman Yim Sovann yesterday said the party knew nothing about the attack. ”The prime minister has many opponents,” he said.

Undersecretary of state for the Ministry of Posts and Telecommunications Chun Vat said the ministry was waiting for data from the administrator of Hun Sen’s page to locate where the hack originated.

A Cambodian branch of Anonymous hacked at least 30 state website following the disputed 2013 election; however, the group went quiet after five of its alleged members were arrested. Two of the men were released after agreeing to work for the state’s cyber security team.

Niklas Femerstrand, a Phnom Penh-based cybersecurity and networking consultant, said the hackers likely used other people’s software to exploit a flaw in the site’s Joomla software, which was publicised six months ago, at which time an upgrade to fix the vulnerability was made available. “It’s nothing serious,” Femerstrand said.

“Had the prime minister not addressed this, chances are no one would have heard of it.”

Additional reporting by Shaun Turton