Australian Open champion Sharapova is 10-0 this season after picking up two Fed Cup wins against Israel earlier this month following her triumph in Melbourne, but world number 126 Voskoboeva, who has yet to reach a quarter-final on Tour, became the first player this year to take a set off the 23-year-old world number five.

Three-time Grand Slam champion Sharapova regained her dominant form in an uneventful third-set triumph and will face Thai qualifier Tamarine Tanasugarn, who upset 14th seed Amelie Mauresmo 7-6 (9-7) 7-5 in the next round.

Top-seeded Ana Ivanovic, runner-up to Sharapova at the Australian open, also returned to action Wednesday with a 6-3 6-1 win over Olga Govortsova.

World number three Ivanovic, seeking her first Tour win since Luxembourg in September, will face Agnieszka Radwanska, who beat Tathiana Garbin 6-3 6-3, in the next round if she recovers sufficiently from an ankle injury suffered after she slipped on the baseline towards the end of the match.

"It definitely hurts a lot and I have difficulty stepping on it," said Ivanovic. "I'll have to wait and see how it reacts overnight, but honestly it's very questionable for the next round. I was a little bit scared and thought I couldn't finish the match. I just took my chances and don't know how I managed to finish. I knew I had to go for my shots because I couldn't run or go into deep rallies."

World number two Svetlana Kuznetsova, runner-up to world number one Justine Henin in her first event of the season in Sydney before suffering a third-round exit at the Australian Open, opened with a 7-5 7-5 victory over Nathalie Dechy of France.

Kuznetsova reached the final last year before losing to Henin and will face Sybille Bammer, a 3-6 7-5 6-4 winner against Monica Niculescu, in the next round.

"It was very, very difficult because of the wind," said Kuznetsova. "Which made it so difficult to control the ball and I'm just happy to get through such a tough match. Nathalie played really well in the middle of the match and I feel pleased to have kept my concentration and made it through."

Elsewhere, Jelena Jankovic of Serbia and sixth-seeded American Venus Williams also advanced, while the first major upset of the tournament came as China's Li Na recorded a hard-fought 7-6 (9-7) 6-4 victory over fifth seed Anna Chakvetadze.

Jankovic downed Russian qualifier Yaroslava Shvedova 6-1 3-6 6-3 to set-up a third round duel with Ai Sugiyama of Japan - a 4-6 6-4 6-0 winner over qualifier Ayumi Morita, while Williams easily dispatched Italy's Karin Knapp 6-2 6-3 to move into a meeting with Dominika Cibulkova, who beat ninth-seeded Patty Schnyder 6-3 6-4.