The Russian 400-metre runner Nadezhda Kotlyarova has said she has tested positive for the banned substance meldonium.

Ms Kotlyarova told Russia's Tass agency that she failed a drugs test last month at the Russian indoor championships, the Associated Press reported.

The 26-year-old athlete protested her innocence, calling the recent spate of positive tests by for the endurance-boosting meldonium an "injustice".

Russian tennis star Maria Sharapova is the most high-profile athlete to have been caught up in meldonium doping row.