India's Commonwealth Games weightlifting gold medal winner Ravi Kumar Katulu has been banned for four years after failing a drug test, a top anti-doping official told AFP on Tuesday.

Cuban discus thrower Yarelys Barrios has been stripped of her Olympic silver medal from the 2008 Beijing Games after failing a retroactive drug test, the International Olympic Committee (IOC) said on Thursday.

Maria Sharapova's multimillion dollar business empire has been plunged into turmoil as sponsors began severing ties with the Russian tennis star a day after she admitted failing a drug test.

Russian tennis star Maria Sharapova said on Monday she had failed a drug test at the Australian Open due to a substance she was taking for health issues, leading longtime sponsor Nike to announce it was suspending ties during the investigation.