Third seed Rafael Nadal returned to Grand Slam action with a comprehensive win over Russia’s Mikhail Youzhny.
The Spaniard, 28, won 6-3 6-2 6-2 in his first match at a Grand Slam since Wimbledon following injury and illness.
Nadal beats Youzhny in straight sets
Ivanovic one of eight women's seeds to lose
Federer & Sharapova through to second round
Teenager Kokkinakis beats 11th seed Gulbis
Second seed Roger Federer outclassed Yen-Hsun Lu 6-4 6-2 7-5 while sixth seed Andy Murray beat India’s Yuki Bhambri 6-3 6-4 7-6 (7-3).
Women’s fifth seed Ana Ivanovic suffered a shock 1-6 6-3 6-2 defeat by Czech qualifier Lucie Hradecka.
The Serb was one of eight seeds to lose but second seed Maria Sharapova, third seed Simona Halep and sixth seed Eugenie Bouchard all advanced in straight sets.
Nadal happy with Slam return
Nadal, who is a 14-time Grand Slam winner, had only played eight matches since a shock defeat by Australian teenager Nick Kyrgios at Wimbledon last year.
Before the tournament, he played down his chances of winning a second Australian Open title but showed glimpses of his best against world number 49 Youzhny.
“I was a little bit under doubt before, but I think I played without making too many mistakes and the only way to get better is to win more matches so it will probably help me,” said Nadal.
“In general I was working well, returning well and I just need to build a little bit, such as being more dynamic with the movements sometimes. But for the rest I am more or less happy.”
Ivanovic one of eight seeds ousted
Serbia’s Ivanovic appeared close to tears as she dissected her shock first-round exit against Hradecka in front of the post-match media.
“I think the whole match I didn’t really feel like myself out there. I had some issues. You know, it’s probably the worst thing that could happen,” she said.
But the 2008 runner-up was not the only seeded female to suffer an opening-day exit, with a quarter of the seeds falling.
Two-time Grand Slam champion Svetlana Kuznetsova, former Wimbledon finalist Sabine Lisicki, ninth seed Angelique Kerber, 16th seed Lucie Safarova, Swiss teenage sensation Belinda Bencic, Spain’sCarla Suarez-Navarro and Russia’s Anastasia Pavlyuchenkova also saw their hopes ended.
Read more at BBC Sport