Mauresmo has only recently returned after a lay-off for surgery

The top seed was playing her second tournament since appendix surgery and twice failed to take match points.

"I guess I didn't keep the intensity the way I should have," she said.

"I have nothing much to say but that I'm just disappointed, and obviously I guess the lack of matches showed a little bit at that moment."

Stosur had not even won a set in their previous five meetings but kept her head as Mauresmo missed match points in the ninth and 13th games of the deciding set.

Mauresmo saved a Stosur match point herself, before the Australian successfully challenged a call on a Mauresmo return, which turned out to be long.

That set up Stosur's second match point, which was converted when Mauresmo put a forehand return out.

"It went game-for-game until the third set, I had to keep fighting, try my best and see," said Stosur. "I pulled it out in the tie-breaker."

Second seed Svetlana Kuznetsova and third seed Jelena Jankovic eased through, with straight-sets wins over Mara Santangelo and Tamira Paszek respectively.

Last year's runner-up Dinara Safina reached round three after a bizarre start to her game with Kaia Kanepi.

There were 10 breaks of serve in the first 11 games before Safina sealed a 7-6 (7-5) 6-2 win.