The World Athletics Championships have been rocked by a drugs scandal after top coach Alberto Salazar was banned for doping, dealing a fresh body blow to the image of track and field at the sport’s showpiece event in Doha.

Salazar, best known for coaching Britain’s four-time Olympic champion Mo Farah, was handed a four-year ban by the United States Anti-Doping Agency (USADA) for a catalogue of drugs violations.

The 61-year-old Cuban-born American was suspended following a years-long investigation by USADA and a prolonged battle behind closed doors, the agency said.

Jeffrey Brown, a Texas endocrinologist who treated many of Salazar’s athletes at his Nike-backed Oregon Project, was also suspended for four years.

Salazar, who denied the allegations against him, was barred from attending any World Championships venues after having his credentials deactivated, the IAAF confirmed Tuesday.

Salazar is not a member of the United States Track and Field Federation team in Qatar, but several athletes linked to his Nike Oregon Project training group are competing at the championships.

They include the Netherlands’ Ethiopian-born runner Sifan Hassan, who romped to victory in the women’s 10,000 metres on Saturday.

United States runners Donovan Brazier and Clayton Murphy, both Oregon Project athletes, will compete in Tuesday’s 800m final.

None of the athletes taking part at the world championships linked to Salazar have been found guilty of doping offences, and none were implicated in USADA’s 134-page summary of the case.

The international Athletics Integrity Unit watchdog meanwhile notified athletes with links to Salazar to cease communication with the coach. (AFP)