Defending champion Serena Williams [Images] issued an ominous warning to her Australian Open rivals with an impressive 6-3, 6-1 second round win over France's [Images] Camille Pin on Wednesday.

The 13th seeded American had appeared to be struggling for fitness and form as she stumbled to a three-set victory over Li Na in the opening round, but her 49-minute destruction of the unseeded Pin proved that she remains anything but a spent force.

Although she has a relatively low seeding after missing most of last season through injury, Williams is lurking as the woman to beat in a top half of a draw packed with the sport's biggest names.

Williams's compatriot and top seed Lindsay Davenport [Images] booked a third-round encounter against 25th seed Maria Kirilenko with a hard-fought 7-6, 6-3 victory over Karolina Sprem.

World number one Davenport was not at her best against her Croatian opponent but was able to raise her game when it mattered.

"I think it was great for me [because] I think that I was able to come through not playing perfect tennis," Davenport told reporters.

"I wasn't panicked and I wasn't uptight about anything."

On a day when several leading women's seeds scored impressive wins, 2004 champion Justine Henin-Hardenne of Belgium beat Hana Sromova 7-6, 6-1 to confirm her position as tournament favourite.

The Czech provided eighth seed Henin with some stubborn resistance in the opening set but her challenge faded quickly when she injured her left ankle and was unable to move around the court as freely.

Henin has replaced compatriot Kim Clijsters [Images] as the bookmakers' favourite to win the title after a brilliant start to the season and is yet to drop a set in her two matches so far.

Four Russian woman all won on Wednesday with two more, Maria Sharapova [Images] and Elena Likhovtseva, yet to play.

The 2004 US Open champion Svetlana Kuznetsova continued her revival after a poor 2005 with a 6-2, 6-7, 6-2 victory over Arantxa Parra to set up a third round meeting with Mara Santagelo.

Sixth seed Nadia Petrova beat Martina Muller in straight sets to set up a third round contest against Italy's [Images] Maria Elena Camerin, while Kirilenko defeated Galina Voskoboeva and Elena Vesnina beat Julia Schruff to face Olga Savchuk of Ukraine.

Williams plays Slovakia's Daniela Hantuchova [Images] after the 17th seed beat Akgul Ananmuradova 6-4, 6-1.

There were two early surprises in the men's event with 13th seed Robby Ginepri and 17th seed Radek Stepanek both losing in five sets.

Ginepri fell 2-6, 5-7, 6-4, 6-3, 6-3 to Denis Gremelmayr of Germany [Images] while Marcos Baghdatis of Cyprus eliminated Stepanek 6-4, 6-3, 3-6, 0-6, 7-5.

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