Prime Minister Hun Sen appeared to foreshadow more arrests yesterday, warning that the government’s crackdown on “rebellion” would not end with the jailing of opposition leader Kem Sokha.

Speaking at the inauguration of a hotel in Siem Reap province, the premier claimed “rebels” were planning to launch a so-called colour revolution, and that Sokha’s purported collusion with the US was only the tip of the iceberg.

The Cambodia National Rescue Party president was arrested a month ago on accusations of treason based on a video of a 2013 speech in which he describes receiving assistance from the US in formulating political strategies. If found guilty, he could face up to 30 years in prison.

“I want to confirm that it is not done yet with the arrest of only one person, as there is a cluster,” Hun Sen warned, calling the purported rebels “foreign slaves”. “We will not let you continue to betray and destroy the nation and peace.”

Though he stopped short of explicitly naming the CNRP, the premier alluded to a “city rebellion” in the offing, appearing to liken it to opposition-backed protests following the disputed elections in 2013.

“The city rebel is staging a colour revolution and it cannot be allowed to take place,” he said. “You have done it and failed, but you are prepared to continue doing it.”

In a thinly veiled threat, Hun Sen referred to “senior officials” who had “made rude comments” in Kampong Thom, Preah Vihear and Siem Reap – locations coinciding with speeches given by CNRP Deputy President Mu Sochua in recent days.

Reached by phone, government spokesperson Phay Siphan said the government was “monitoring closely” the activities of groups and individuals who were allegedly involved in what he also described as an urban rebellion. He said the government had a mandate to crack down on these activities.

“We learned from the Middle East,” he said. “But the government has proof that . . . a group tries to stage anarchy on the streets, especially in the city.”

He added that there were ongoing investigations into allegedly traitors, but when asked who was under investigation, he replied: “Why would you want to know this? It’s about national security. Are you a spy?”

Sochua said that she and her team had been personally monitored by three to five plainclothes policemen over the past few days.

“In Siem Reap we were followed from the minute we got in,” she said. Sochua said she and her team, including CNRP parliamentarian Mao Molyvann, were followed by people on motorbikes when they went for meetings, lunch and dinner.

Sochua said that in Oddar Meanchey, at least five plainclothes agents monitored their meetings and took notes and pictures.

She added that as they were leaving Oddar Meanchey, they were followed by a police car. When her convoy stopped the car to ask why they were being followed, she said the officers told her that “we wanted to make sure you were safe”.

As for threats of arrests, she said that she did not know which officials were targeted and wasn’t scared of intimidation. “I worry only about one thing: about my nation, which falls into an authoritarian power,” she said.

“We can see the election without the participation of the biggest opposition party in 2018. Can the election be called free and fair?”

Hun Sen in his speech also lashed out at the supposed hypocrisy of the international community, which he maligned for having previously recognised at the UN the murderous Khmer Rouge – to which he once belonged – only to condemn him now for the arrest of a purported traitor. “I only enforce the existing law,” the premier said. “Why can I not [punish treason]? I don’t do it for my own life, but for the happiness of the whole country.”

The international community has repeatedly called on the prime minister and other senior government officials to respect the presumption of innocence and not make comments on Sokha’s alleged guilt.

The United Nations, for its part, last week passed a resolution condemning Sokha’s arrest and expressing “serious concern over the recent deterioration of the civil and political environment in Cambodia”.

Hun Sen then appealed for the public to “unite” to protect the political stability of Cambodia. “Wanting to protect the achievements, jobs and works that we have right now, it is necessary for us to jointly maintain peace and stability. Or else, a problem will happen,” he said.

Ear Sophal, a professor of diplomacy at Occidental College, said the premier’s threats to the opposition were in many ways familiar, but that his description of the CNRP was unjustified.

“Only the term ‘rebels in the city’ is new, but then the only rebels in the city historically were the Khmer Rouge who came in on 17 April, 1975,” he said via email. “Rebels have weapons. The only weapons the CNRP has are words.”