The Belorussian, who lost to Serena in the Wimbledon semifinals, will next face Maria Jose Martinez Sanchez of Spain.

CNN: Williams sisters progress in Olympic tennis events

Defending champion Serena snatched the first set against Maria Jose Martinez Sanchez and then survived a second-set fightback before prevailing 6-3 7-5.

BBC: Serena and Venus battle through

Thursday's quarterfinals see Serbian sixth seed Jelena Jankovic taking on Russia's Alisa Kleybanova and Australian eighth seed Samantha Stosur playing Spain's Maria Jose Martinez Sanchez.

CNN: Radwanska to face friend Wozniacki in Indian Wells semis