MELBOURNE - Novak Djokovic overcame persistent hamstring issues, heckling from fans and pesky French qualifier Enzo Couacaud on Thursday to reach the Australian Open third round, but women's second seed Ons Jabeur crashed out.

On a dramatic day four, where several high profile men's players were eliminated, Djokovic defied the obstacles to thwart 190th-ranked Couacaud 6-1, 6-7 (5), 6-2, 6-0 in three hours and four minutes.

"There was a lot happening tonight and Enzo deserves credit, he played some really great tennis, especially in the second set," Djokovic said.

In a fiery match, Djokovic continued his tempestuous relationship with Australian fans after being jeered by a group of colorfully dressed spectators.

After a heated confrontation with the umpire early in the fourth set, where he complained about a "drunk" spectator, Djokovic got his wish with four fans escorted out.

"You just have to deal with it. One of those circumstances and situations where things are maybe not going perfectly your way. But that's sport," Djokovic said.

As he has done numerously in his legendary career, Djokovic lifted in adversity and quickly ended Couacaud's resistance to book a third round clash with Bulgaria's Grigor Dimitrov.

Djokovic's troublesome hamstring, which he injured ahead of the tournament, was heavily strapped and he required a medical timeout late in the second set.

But 35-year-old Djokovic, who hit 63 winners, marched on as he seeks his 10th Australian Open title and record-equalling 22nd Grand Slam trophy.

Fourth seed Djokovic remains the overwhelming favorite, with some of his main rivals heading home.

One day after defending champion Rafael Nadal hobbled out, second seed Casper Ruud was upset by American Jenson Brooks 6-3, 7-5, 6-7 (4), 6-2.

There were parallels with the shock exit of top seed Nadal, who succumbed to a troublesome hip injury in his straight-sets defeat to Brooks' compatriot Mackenzie Macdonald.

Norway's Ruud battled pain in his abdominal and required a medical timeout in the second set.

"It's something that has actually been with me for around two years. It just sort of tightens up my left side from serving," Ruud said of the injury.

"It didn't affect me a lot, but I felt it a little bit in the second set. I hope it's nothing serious."

The result ended the hopes of an elusive Grand Slam title for Ruud and his bid to claim the world number one ranking from Carlos Alcaraz, who is sidelined from the tournament with injury.

There were casualties for other leading players, with eighth seed Taylor Fritz packing his bags after losing to Australian wildcard Alexei Popyrin 6-7 (4), 7-6 (2), 6-4, 6-7 (6), 6-2.

Alexander Zverev, the 12th seed, crashed out to American Michael Mmoh 6-7 (1), 6-4, 6-3, 6-2.

The women's draw also had a major upset with Jabeur, last year's Wimbledon and US Open finalist, knocked out in the second round by 86th ranked Marketa Vondrousova 6-1, 5-7, 6-1 in one hour and 42 minutes.

After a shaky start, Jabeur appeared to turn the tide by taking out a tight second set before slumping to defeat against Vondrousova, who showcased the type of form that saw her reach the French Open final in 2019.

Jabeur's exit has opened the door for fourth seed Caroline Garcia, who battled past 2021 US Open finalist Leylah Fernandez 7-6 (5), 7-5 in one hour and 52 minutes.

Garcia of France has had a career revival in the last 12 months and fended off dangerous 20-year-old Fernandez in a high-octane contest.

In-form Aryna Sabalenka underlined her burgeoning title credentials with a 6-3, 6-1 victory over American Shelby Rogers.

Having won the recent Adelaide International, a confident Sabalanka hit 32 winners to overpower the 53rd-ranked Rogers.

China's top seeded women's player Zhang Shuai swept past Petra Martic 6-3, 6-3 in 73 minutes.

Zhang, the 23rd seed, set up a third round clash with American qualifier Katie Volynets, who stunned ninth seed Veronika Kudermetova 6-4, 2-6, 6-2.

The result was achieved exactly seven years after her first victory at a Grand Slam, which kick-started Zhang's fairytale quarterfinal run at the Australian Open in 2016.

"I am always feeling good at the Australian Open because it is special for me," Zhang said. "I'm feeling so happy. I think all the hard work is working and made me improve a little bit every day."