The single punch was so powerful that it knocked the officer unconscious "for at least a minute" and caused him to suffer temporary memory loss, according to a report by TODAY newspaper.

On Tuesday, Devesh Raj Rajasegaran, 24, was sentenced to five weeks in prison. He had pleaded guilty in March this year to one count of voluntarily causing hurt.

Devesh will appeal against the sentence, according to the report.

The court heard that the victim was one of four police officers dispatched to an area in Circular Road in the central business district on June 25, 2022 after a member of the public informed them around 3 am of "more than 10 people having an argument".

Prior to this, Devesh and his friend Eeshwar Ravi were drinking alcohol nearby.

When the police arrived, they spotted a group of individuals including Devesh and Eeshwar involved in a "commotion" in Circular Road.

The officers, who were wearing civilian clothes at the time, approached the group, identifying themselves as police officers. Three of them were volunteer police officers.

While the victim and another officer were interviewing a member of the group, Devesh approached them to confront the individual who was being interviewed. Soon after, Devesh threw a punch, hitting the police officer on the left side of his head.

Deputy Public Prosecutor Brian Tan said in court documents, "The accused was intoxicated when he punched the victim. As a result of the accused's punch, the victim lost consciousness for at least a minute."

The officer was later taken to the Singapore General Hospital by ambulance. Between the time he was punched and when he reached the hospital, he drifted in and out of consciousness several times.

The victim was given seven days' hospitalisation leave and reported suffering temporary loss of memory and bad headaches for at least three days after the incident.

For voluntarily causing hurt, Devesh could have been jailed for up to three years, ordered to pay a fine of up to SGD5,000 or both.