Botswana medal hope Isaac Makwala has accused the IAAF of "sabotage" after he was excluded from Tuesday night's 400 metres final on medical grounds following a bout of norovirus.
The 30-year-old had been expected to challenge favourite and Olympic champion Wayde van Niekerk of South Africa over one lap. Van Niekerk won gold on Tuesday night.
Video footage showed Makwala was prevented from entering the warm-up track and Botswanan officials criticised the IAAF for their heavy-handedness and lack of communication.
Makwala told ITV News: "They said I had food poisoning - which I don't have. I was not tested for that.
"They didn't even want to listen to me. They said 'no, you can't run because you are sick.'
"Sometimes I think maybe this is sabotage."
Makwala claimed had he been British he would have been permitted to compete.
He said: "I asked myself 'what if I was a Great British guy, would they not allow me to run?'
"I don't think they would not allow me to run. If they saw the guy had potential they are going to allow him to run.
"It's only because I'm not a Great British athlete."
Athletics' world governing body has defended its decision, saying it was taken to contain the contagious illness.
The IAAF said in a statement issued moments before the final: "The IAAF is very sorry that the hard work and talent of Isaac Makwala won't be on display tonight but we have to think of the welfare of all athletes.
"The athlete was diagnosed with an infectious disease on Monday.
"As per UK health regulations, it was requested that he be quarantined in his room for 48 hours, a period which ends at 1400hrs tomorrow (August 9).
"These procedures are recommended by Public Health England and were clearly explained to the teams in writing on Sunday (August 6) and in person to the Botswanan delegation, a member of which was present with many other representatives of teams at a meeting that took place at the Guoman Tower Hotel on Sunday."
Former 400m World and Olympic champion and world record holder Michael Johnson questioned the decision to exclude Makwala.
Johnson told the BBC: "There is the elephant in the room - Wayde van Niekerk's only challenger has been pulled out of both the 200m and 400m. The conspiracy theories will come out of the silence."
Botswana team officials dispute the IAAF's version of events and criticised the communication from the world governing body.
Makwala had been given medical dispensation to withdraw from the 200m heats on Monday night.
Without a valid reason for pulling out, he could have been disqualified from the 400m final - an event he was forced to miss.
Botswana national sports commission chief executive Falcon Sedimo said the team found out about Makwala's exclusion through the media.
Sedimo added on the BBC that Makwala had not been subject to medical tests on Tuesday.
The Botswana team and IAAF dispute the version of events which led to Makwala's exclusion.
Briton Simon O'Brien, who is part of the Botswana medical staff, said on the BBC: "There was no-one (from the Botswana team) present. Isaac was in the tent.
"We were informed only when one of the officials from the IAAF came over and tried to search for me."
O'Brien said Makwala was sick once as he alighted the bus to the stadium ahead of his 200m heat on Monday, but reported that his heart rate of 60 beats per minute and body temperature of 36.9C were "completely normal".
"He's fit, he's very well, he's prepared to run, and he's just being kept away by the IAAF," O'Brien added.
The bizarre situation arose on a day when Public Health England disclosed norovirus had been diagnosed following illness at one of the official competition hotels.
London 2017, the championship organisers, announced on Monday night that several London 2017 competitors - staying at the same official team hotel - had suffered gastroenteritis.
A spokesperson for the Tower Hotel on Tuesday morning insisted it was "not the source of the illness".
Public Health England on Tuesday said around 30 people had been affected, with laboratory testing revealing norovirus in two cases, and later told Press Association Sport that it believes there are connected cases at other hotels accommodating those involved in the championships.
One Irish athlete, Thomas Barr, a 400m hurdler, has been affected and Athletics Ireland said its athletes yet to compete and yet to arrive in London will be housed in alternative accommodation so as not to mix with anyone potentially infected.
Norovirus is an unpleasant but rarely serious illness often caught through close contact or by touching contaminated surfaces or objects.
It can result in vomiting and diarrhoea, and those affected are encouraged to drink fluids to avoid dehydration.
Most people make a full recovery within one or two days, but it may be debilitating for those affected athletes scheduled to compete here.