World Athletics Championships
IAAF confirm provisional bans for two athletes Getty Images

Kenyan athletes Koki Manunga and Joyce Zakary have tested positive for banned substances at the Worlds Athletics Championships in Beijing, the International Association of Athletics Federations (IAAF) has confirmed.

Manunga, 21, and Zakary, 29, both 400m runners, have been handed provisional bans following pre-competition tests which took place 20 August August 20 and 21 August before the championships began. World athletics's governing body would not disclose which substances they tested positive for.

"The IAAF rules dictate that the IAAF is only able to make a public disclosure once this provisional suspension is in place," said the governing body.

"These targeted tests were conducted by the IAAF at the athlete hotels during the pre-competition phase. The IAAF will not discuss the details of the cases as they progress through the results management process."

Zakary ran a new national record in the 400m heats but then pulled out of the semi-finals on Tuesday 25 August. Manunga failed to qualify for the 400m hurdles finals after finishing second to last in heats.

Kenya currently top the medals table in Beijing with four golds, three silvers and two bronze medals.