World number one Serena Williams continued her march towards a first Western and Southern Open title, easing into the quarter-finals of the Cincinnati tournament with a 6-2, 6-2 demolition of 13th-seeded Italian Flavia Pennetta.

The 17-time grand slam winner was joined in the last-eight by second seeded Romanian Simona Halep, who defeated Czech Lucie Safarova 6-4, 7-5.

Williams served eight aces and broke the Italian five times in their hour-long match.

"I have a lot more confidence," Williams said. "I feel more relaxed. Overall feel a lot better. I'm playing a lot better."

Earlier, French Open champion Maria Sharapova also advanced with a victory against Anastasia Pavlyuchenkova 6-4, 7-6.

Sharapova's win sets up a match against Halep.

Caroline Wozniacki and Jelena Jankovic also advanced with straight set victories. The Dane saw off sixth-seed Angelique Kerber 7-5, 6-2 while Jankovic beat American Sloane Stephens 7-6, 6-4.

Other results:

Agnieszka Radwanska (Poland) beat Sabine Lisicki (Germany) 6-1, 6-1
Ana Ivanovic (Serbia) beat Svetlana Kuznetsova (Russia) 6-2, 2-6, 6-3 

Source: Reuters