Rio de Janeiro: International Olympic Committee vice-president and Australian Olympic chief John Coates has described Rio's Games as "the most difficult we have ever encountered".

The pointed take follows his stinging declaration, in April 2014, that the host city's preparations were "the worst" he'd experienced; topping Athens in 2004.

The Russian doping hornets nest aside, myriad off-field issues have marred Rio's Games, from minor problems with food supplies at competition venues to the genuinely alarming damage inflicted on an official media bus travelling between Deodoro and the main press centre that left three passengers injured.

Games organisers said on Thursday the release of a report that would prove the damage was caused by stones is imminent. The IOC and Rio authorities are insisting that security is a priority and that military protection has been increased around the city and Games venues.