The 28-year-old rider, who has not been identified, died after the accident on the slip road outside the Main Press Centre in East London just after 730pm on Wednesday night.
Despite frantic efforts by paramedics, the cyclist was pronounced dead at the scene just over 30 minutes later.
A man in his mid sixties was arrested on suspicion of causing death by dangerous driving.
| A damaged bicycle lies next to an Olympic Games|
bus after an accident that killed the cyclist
Witnesses reported horrific scenes after seeing the man lying underneath the decker-bus on the A106 about a mile outside the Olympic Park as his mangled white and chrome racing bicycle lay nearby.
It remained unclear on Wednesday night whether the cyclist was involved in the Games - either as an athlete, official or spectator - or was a member of the public.