A Vietnamese man was found with his head severed at a Jalan Sultan hotel early yesterday morning.

Mr Nguyen Ngoc Duy, 23, is believed to have fallen from a 15th-floor room at Hotel Boss at about 2.30am.

His body landed on the fifth floor but his head was found outside a fourth-storey eatery, Chinese evening daily Lianhe Wanbao reported.

Police are investigating the case as an unnatural death.

The Straits Times understands that no foul play was involved in the incident.

Lianhe Wanbao reported that the room was booked by Mr Vu Truong An, 21, an Institute of Technical Education student, who was having a staycation with five friends, including Mr Nguyen.

An argument reportedly broke out between Mr Vu, who is also from Vietnam, and Mr Nguyen.

After Mr Nguyen fell, Mr Vu reportedly rushed to seek help from hotel staff, who called the police.

Mr Vu was taken to hospital with a slash wound on his head. He is believed to be in stable condition.

A night-shift supervisor at Founder Bak Kut Teh, a restaurant on the hotel's first floor, who wanted to be known only as Madam Lim, told The Straits Times that she saw eight police cars.

"It was a curious sight. I didn't know what happened as I didn't hear anything. Later on, I saw a hearse arrive," she said.

The hotel later put up a notice informing guests there was no access to the fourth storey, which also has a swimming pool and a gym, due to an "unforseen situation".

But operations on that floor resumed by evening and many guests were unaware of the incident.

The hotel declined to comment.