I admit that we are unhappy, we could have done better,' said Diack. 'But this is definitely not a case of racism.'

The whole of South Africa rallied behind the athlete, who won the gold a few hours after the IAAF confirmed that the tests had started, with results due within the next weeks.

South African athletics boss Leonard Chuene allegedly threatened to resign from the IAAF Council during a stormy meeting Saturday.

Diack praised the overall running of the championships which brought together 1,984 athletes from 201 countries and attracted some 400,000 fans to the Olympic Stadium as the biggest sports event of the year.

Diack praised the spread as 34 countries medalled ahead of the concluding eight finals Sunday and 55 countries had athletes in finals.

IAAF spokesman Nick Davies said that 900 of the planned 1,000 doping tests have been conducted. There have been two positive tests so far, involving Nigerian 400 metres hurdles runner Amaka Ogoegbunam and Moroccan steeplechaser Jamal Chatbi.