Other seeded players to progress were China's Na Li (16), Daniela Hantuchova (22) and Shahar Peer (29).

CNN: Williams pair continue smooth progress

Fourth seed Venus followed up her opening win over Patty Schnyder with another routine straight-sets victory, defeating Israeli 16th seed Shahar Peer 6-3 6-4.

CNN: Serena and Venus headed for Rome semifinal clash

Meanwhile, Russian second seed Maria Sharapova was given a scare, dropping the opening set before rallying to defeat Israel's Shahar Peer 4-6 6-3 6-3.

CNN: Serena returns with victory in Miami