Day five at the Australian Open

MELBOURNE (Reuters) - Six-time champion Roger Federer was pushed to the brink by unseeded Australian John Millman but the Swiss prevailed in a fifth-set tiebreak on Friday to reach the Australian Open fourth round on a day of huge upsets at Melbourne Park.

Federer won 4-6 7-6(2) 6-4 4-6 7-6(8) to secure his 100th Australian Open match win after an intense encounter with world number 47 Millman lasted over four hours.

Earlier, Serena Williams and defending champion Naomi Osaka suffered shock defeats that tore open the women's draw.

Williams' latest bid for a record-equalling 24th Grand Slam was ended by China's Wang Qiang, who won 6-4 6-7(2) 7-5.

American teenager Coco Gauff stunned Osaka in straight sets, 6-3 6-4, ranking the victory as "somewhere around the top" of her biggest wins.

Former world number one Caroline Wozniacki brought the curtain down on her glittering career as she suffered a 7-5 3-6 7-5 defeat at the hands of Tunisia's rising star, Ons Jabeur.

(Compiled by Greg Stutchbury, Shrivathsa Sridhar and Hardik Vyas; Editing by Sam Holmes and Muralikumar Anantharaman)