A man is in custody after a stabbing in the Brisbane CBD on Thursday morning.

Emergency services were called to the corner of Elizabeth and William streets just before 5am.

The scene of the stabbing near Treasury Casino in the heart of Brisbane on Thursday morning. Credit:Jess Millward - The Today Show

A Queensland Ambulance Service spokesman said three male patients were taken to the Royal Brisbane and Women's Hospital.

The first patient suffered an abdominal wound and was taken to hospital in a serious condition with the high acuity response unit on board.