The International Testing Agency (ITA) tweeted on Friday it has conducted more than 3,100 doping tests so far at the Tokyo Olympics.
The ITA said more than 2,240 athletes from 150 countries have been tested with half of the tests in-competition and the other half out-of-competition.
It said cycling, weightlifting, swimming, rowing and athletics were among the 10 sports, with the most tests at the Games which run until Aug. 8.
The U.S, China, Australia, Britain and hosts Japan were among the top 10 tested nations along with the athletes from Russia.
The tweet did not say whether there had been any positive tests at the Games.
The ITA also conducted an extensive pre-Games testing programme, saying it had implemented around 80 per cent of some 25,000 recommendations from sports federations and national anti-doping agencies.