Patrick Baumann, the secretary-general of basketball's world governing body FIBA who was seen as a potential International Olympic Committee president, has died.
Baumann is thought to have suffered a heart attack while attending the Youth Olympics in Buenos Aires, Argentina. He was aged 51.
Basketball Australia chairman Ned Coten expressed the thoughts of the Australian basketball family.
"Our deepest sympathy and condolences are with Patrick's wife and family at this very difficult time," Coten said.
"The world of basketball has lost a giant tonight and we are shocked at this sudden and unexpected news.
"Patrick's vision and astute leadership has seen the sport of basketball grow all over the world. Our game has lost an inspirational leader and Australian basketball has lost a great friend."
IOC president Thomas Bach said: "This is a great shock, which has hit us all very hard. We can hardly believe this terrible news. Particularly since, even today, we have seen him working hard, as we always knew him, for the sport he loved.
"We lose a young and sympathetic leader full of hope who was standing for the future of sport. Our thoughts are with his wife, his children and his family."
Baumann was FIBA's top administrator for 15 years and an International Olympic Committee member since 2007.
Flags will be flown at half-mast at IOC offices in Buenos Aires and its home city of Lausanne, Switzerland. The IOC said a memorial will be held in the athlete village in Buenos Aires.
A lawyer from Switzerland, Baumann had taken an increasingly important role in Olympic circles.
