SINGAPORE - Three Britons of Vietnamese descent are on trial for the alleged rape of a 23-year-old woman at the Carlton Hotel in Bras Basah Road on Sept 10 last year.

Tam Thanh Khong, 22, together with Michael Le and Vu Thai Son, both 24, had flown here from Britain on Sept 9 to attend the two-day dance music festival Ultra Singapore. They were also here to celebrate Khong's brother's stag party.

They are accused of taking turns to rape the Malaysian woman, who was drunk and asleep at the time. Khong and Vu are also accused of digitally penetrating the woman.

A friend of the trio, Mr Ahn Viet Trinh, also known as Richard - a 24-year-old British citizen also of Vietnamese descent - had met the woman at nightclub Zouk.

Mr Ahn and the woman were at the club sometime after midnight with friends, and among Ahn's friends were the three accused.

The woman, who cannot be named due to a gag order, worked as a marketing and corporate communications officer in Malaysia and had arrived in Singapore on Sept 9.

That night, Mr Ahn and her struck up a conversation, and when she suggested they return to his hotel room in Carlton Hotel, he readily agreed. By this time, she was drunk.

They had consensual sex from about 2.30am, and the woman fell asleep in the room, also shared by Mr Ahn's other friends who were not around at the time.

Deputy Public Prosecutor G. Kannan said that around 4am, Mr Ahn allowed Khong to enter the room. Khong then allegedly raped the woman, who was not awake.

Khong left the room and "like clockwork", said DPP Kannan, Vu entered the room to take his turn around 4.25am. He too allegedly raped the woman.

When Vu left the room, Le entered "within the minute" at 4.50am, undressed and got onto the bed with the victim, who was naked. He then allegedly raped the woman who woke up midway and confronted Le. A heated exchanged ensured, and he left the room around 5.05am.

When Mr Ahn returned to the room around 5.20am, the woman confronted him as she suspected that he was involved. However he claimed to have no knowledge of it, and the victim left the hotel around 6.30am.

Mr Ahn had been under investigation along with the three accused. His passport had been impounded by the police, but he left jurisdiction illegally before investigations were completed.

The prosecution will call 24 witnesses throughout the trial. The victim will also be testifying in-camera, and the prosecution will be submitting CCTV footage from the hotel that captured the three men entering and leaving the room where the alleged rape happened.

Messages exchanged between Le and his friends in a chat group where he purportedly admitted to having sex with the victim will also be presented to the court.

Mr Shashi Nathan is acting for Thanh while Le and Vu are represented by Mr Kalidass Murugaiyan and Mr Ramesh Tiwary respectively.

The trial will resume at 3pm on Tuesday (Aug 1).