Kenyan runners Koki Manunga and Joyce Zakary have tested positive for banned substances at the World Athletics Championships in Beijing.

Manunga, who was the silver medallist in her event at the African championships, competed in the women's 400m hurdles event earlier this week, but was eliminated after finishing seventh in her heat.

Zakary had broken the Kenya national record in her 400m heat earlier this week with a time of 50.41s before missing the semi-finals.

Kenya currently top the medal table with four golds, three silvers and two bronzes.