David Chanaiwa (left) and Prak Ou Fie, who were arrested on Tuesday after wrecking their car and then allegedly beating 10 journalists, appear at the Phnom Penh Municipal Court yesterday. Photograph: Sreng Meng Srun/Phnom Penh Post

Prime Minister Hun Sen yesterday fired Yean Sina, an undersecretary of state at the Ministry of Justice, accusing him of taking part in the vicious beating of 10 journalists after a car crash in the capital just past midnight on Tuesday.

Labelling Sina an “old gangster”, the prime minister delivered a scathing assessment of the Funcinpec member’s alleged behaviour – as one of a gang of seven – before revealing he had made the decision to end Sina’s time in government.

“I have already written a letter expelling him from his position and work,” Hun Sen said during a speech at a technology institute. “Old gangsters – the undersecretary of state and a former lawyer, David Chanaiwa – drove these cars, caused an accident and then beat up a group of journalists. I’m waiting to see whether or not these people will evade the law.”

Hun Sen said he would closely monitor legal proceedings again Sina, who has not yet been detained by police, and Chanaiwa, whom Hun Sen knew as the man who had driven a Hummer through public gardens bearing his name.

Chanaiwa, 41, a disbarred lawyer who was sentenced in absentia last year to 18 months in prison for firing his gun – time he didn’t serve – and his nephew, Prak Ou Fie, also known as Ma Ou Fie, 20, were arrested on Tuesday, accused of attacking the television and newspaper journalists.

According to police, the perpetrators had been in two cars that crashed on Monivong Boulevard shortly after midnight and turned on journalists after they arrived on the scene. One man was seriously injured in the attack.

Major Bun Sathya, deputy chief of the Phnom Penh Municipal Police’s minor crimes office, said Ou Fie and Chanaiwa – a Khmer-American who arrived in Cambodia in 1994, served time as a policeman, was once an adviser to Senate President Chea Sim and was banned from the Cambodian Bar Association in 2003 – were charged yesterday and sent to Prey Sar prison.

“David Chanaiwa was charged with intentionally causing injuries and using an illegal weapon,” he said. “His nephew was charged with intentionally causing injuries.”

In an interview with the Post yesterday, Chanaiwa and Ou Fie denied the charges against them and said they had not been drag-racing prior to the crash.

“I did not beat any journalists on that night,” Chanaiwa, the former chairman of the now-defunct Brothers Investment Group, said, adding that the journalists had exaggerated the story. “I deny all accusations against me. This case was a traffic accident, but it was not caused by me.”

Chanaiwa said the only reason he had been at the accident scene was to help his nephew, who was in one of the cars.

“If I had really been involved, I would’ve fled from the scene.”

In relation to his shooting conviction, Chanaiwa said he was appealing the guilty verdict, because he had been in the US at the time of the incident.

“These allegations were made up by the police,” he said. “To find justice, I will appeal to higher courts.”

Seak Vannak, the two men’s defence lawyer, said Chanaiwa’s new charge of using an illegal weapon was not related to the attack on the journalists, adding that his client had been separately convicted in absentia on February 29 to an additional 18 months in prison over another incident.

As for Sina, Major Bun Sathya said a warrant for his arrest would be issued today.

“I think he will be arrested very soon,” he said.

Sina, who is in his forties, could not be reached for comment.