Victoria Azarenka into quarter-finals with Nadia Petrova triumph

Number one seed Victoria Azarenka has moved into the quarter-finals of the women's Olympic singles after a straight-sets victory over Russian 16th seed Nadia Petrova.

With both players holding serve in the opening set it was the Belarusian who came out on top 8-6 in the tie-break to gain the initiative.

The second got off to a bad start for the Australian Open winner when she was broken, but she converted her third break point to level at 4-4.

Azarenka then broke for a second time to complete the turnaround and close out the match 6-4.

She will now face either American Venus Williams or Germany's Angelique Kerber for a coveted semi-final berth.