A 23-year-old police full-time national serviceman (NSF) died yesterday, nearly a week after he was found with a gunshot wound to his head.

The incident happened at the Protective Security Command in Ulu Pandan Road last Monday, the police said in a statement yesterday. His service revolver was found beside him.

The serviceman had reported for duty at 8am last Monday, and had drawn his service revolver from the armoury.

At 3.20pm, he was found with a gunshot wound to his head at the rest area in the Protective Security Command, where he was taking a break before resuming duty.

He was unconscious when taken to the National University Hospital.

Preliminary investigations by the Criminal Investigation Department revealed that the serviceman was heard arguing on the phone shortly before he was found with the gunshot wound.

The police have classified the case as unnatural death, and the circumstances relating to it are being carefully investigated.

No foul play is suspected.

The Straits Times understands that the incident was not work-related.

The police said in their statement: "The police extend our deepest condolences to the family of the late serviceman and are assisting the family in this time of grief."

The Protective Security Command is a specialist unit set up in 2016 to protect security-sensitive locations and provide security coverage at key national events.

The unit has the largest group of full-time national servicemen and operationally ready national servicemen in the Singapore Police Force.