Former Wimbledon champions Venus Williams and Petra Kvitova crashed out of the Australian Open in the first round.

Venus was beaten 6-2, 4-6, 4-6 by Ekaterina Makarova while Kvitova was upset in the first round Thailand's Luksika Kumkhum, 6-2, 1-6, 6-4.

Williams, who suffers from Sjogren's Syndrome which causes fatigue and joint pain, was hampered by back problems last year but declined to blame health issues for the loss.

Kvitova lost in the first round of a Grand Slam for the first time since the 2011 US Open, months after claiming the title at Wimbledon.

Top-ranked Serena Williams extended her winning streak to 23 matches and cruised into the second round of the Australian Open with a 6-2, 6-1 victory over Australian wildcard entry Ashleigh Barty.

Serena, who collected 11 titles including two majors as she won 78 of her 82 matches in 2013, opened this season by defending her title at the Brisbane International and carried the momentum into Melbourne.

Meanwhile, Novak Djokovic began his bid for a fourth consecutive Australian Open singles title with a 6-3, 7-6, 6-1 win over Lukas Lacko.

Elsewhere, Sam Stosur fought back from 4-1 down in the second set to beat Klara Zakopalova of the Czech Republic 6-3, 6-4.

Belinda Bencic, a 16-year-old qualifier playing in her first major after winning two junior Grand Slam titles last year, eliminated Kimiko Date-Krumm in the first round, 6-4, 4-6, 6-3.

Men's results (selected)

David Ferrer (3) def. Alejandro Gonzalez 6-3, 6-4, 6-4

Tomas Berdych def. Aleksandr Nedovyesov 6-3, 6-4, 6-3

Stanislas Wawrinka (8) def. Andrey Golubev 6-4, 4-1, retired

Richard Gasquet (9) def. David Guez 7-5, 6-4, 6-1

Guillermo Garcia-Lopez def. Tommy Haas (12) 7-5, 5-2, retired

Mikhail Youzhny (14) def. Jan-Lennard Struff 6-1, 6-4, 6-2

Women's results (selected)

Li Na (4) def. Ana Konjuh, Croatia, 6-2, 6-0

Julia Goerges def. Sara Errani (7) 6-3, 6-2

Angelique Kerber (9) def. Jarmila Gajdosova 6-3, 0-6, 6-2

Ana Ivanovic (14) def. Kiki Bertens 6-4, 6-4

Sabine Lisicki (15) def. Mirjana Lucic-Baroni 6-2, 6-1

Kirsten Flipkens (18) def. Laura Robson 6-3, 6-0

Source: Agencies