The 2,700 figure, however, relates to tests conducted as part of "unannounced" pre-tournament testing between January 1 and June 13.

FIFA claimed that all 736 players competing at the showpiece event have been tested at least once either before or during competition.

The exact number of tests conducted since matches began on June 14 has not been published, though.

They have also not yet confirmed how many out-of-competition tests are currently ongoing. 

"Every participating player has been tested in unannounced controls ahead of the competition and further systematic tests are performed during the competition," a FIFA spokesperson told the Daily Telegraph.

"The doping controls at the World Cup in Russia are currently ongoing and therefore we cannot provide details at this stage.

"Prior to the competition, from 1 January 2018 till the 13 of June, 2,761 samples were collected by FIFA in unannounced controls. 

"Nine-hundred-and-twelve whole blood samples and 912 serum samples were collected by FIFA in the lead up to the World Cup.

"FIFA collaborated closely with National Anti-Doping Organisations and confederations to have all participating players tested in the lead up to the World Cup in Russia."

FIFA have, however, used the Athlete Biological Passport system since the 2014 World Cup to detect changing blood values from players over time.

All samples are being analysed at the World Anti-Doping Agency-accredited laboratory in Lausanne and FIFA insist that no Russians are involved in the implementation of the programme.

Investigations by ARD and the Mail on Sunday have found FIFA was aware of doping cover-ups in Russian football but chose not to act despite strong evidence.

Reports claimed world football's governing body had proof that samples provided by Russian footballers were manipulated as long as 18 months ago.

It has also been suggested that FIFA were provided with documentary evidence of the involvement of 34 players out of the 154 outlined in the McLaren Report which could have been strong enough to bring sanctions.

This includes allegations that Ruslan Kambolov, who was dropped from the Russian World Cup squad with a supposed calf injury, was among those to have had positive tests covered up.

The world governing body has denied any wrongdoing.

It follows Russia being made to compete under a neutral flag at this year's Winter Olympic Games in Pyeongchang in response to their "systemic manipulation" of the anti-doping system at the previous edition in Sochi. 

Peru captain Paolo Guerrero was only belatedly able to play in the World Cup after a Swiss Tribunal overturned a 14-month drugs ban shortly before the tournament.

Guerrero tested positive for cocaine metabolite benzoylecgonine after his country's 0-0 draw in their World Cup qualifier against Argentina in Buenos Aires on October 6.