German Zverev beaten in five sets by South Korea's Chung, and Thiem progresses to fourth round
Australian Open Day 6: Federer and Djokovic win after Berdych upsets Del Potro
Defending champion Roger Federer continued his dominance over Richard Gasquet to reach the round of 16 at the Australian Open on Saturday.
Second seed Federer beat the Frenchman 6-2, 7-5, 6-4 and will face Hungary's Marton Fucsovics for a place in the quarter-finals.
Novak Djokovic battled with a lower back injury as he claimed his 11th round of 16 appearance here on Saturday.
The six-time champion advanced with a clear-cut 6-2, 6-3, 6-3 win over Spanish 21st seed Albert Ramos-Vinolas in 2hr 21min on Margaret Court Arena.
But there was concern in the Serb's camp when the former world No 1 sought a medical timeout early in the second set for treatment to his lower back.
Djokovic, looking for matches after six months out with right elbow trouble, will next face South Korea's Chung Hyeon in Sunday's fourth round after he shocked Alexander Zverev.
The injury was a fresh concern for the 12-time grand slam champion, whose ranking has slipped to 14 after an inactive second half of 2017.
But Djokovic was workmanlike as he broke the Spaniard's serve five times, although his errors outnumbered his winners 40-37.
"It was a straight sets win, but it was almost two-and-a-half hours, so it wasn't that easy and comfortable on the court," Djokovic said.
Berdych too strong for Del Potro
Veteran Tomas Berdych reached the round of 16 for the 10th time at the Australian Open with a straight sets win over Juan Martin del Potro on Saturday.
The 32-year-old Czech eliminated the 12th-seeded Argentine 6-3, 6-3, 6-2 in 2hr 16min on Hisense Arena.
Berdych, who has played in the semi-finals twice in Melbourne, will face Italian journeyman Fabio Fognini in their first grand slam match in Monday's fourth round.
Berdych served up 20 aces, broke serve seven times and hit 52 winners with 28 unforced errors.
"I think I was well prepared and I stuck with my plan and I'm glad as I can stand here as a winner today," Berdych said.
"Juan Martin is a great competitor and I'm glad he is back after all the injuries that he's had. Tennis was missing him and it's great that he's back."
Zverev suffers shock defeat
Chung Hyeon became the first South Korean man ever to reach the round of 16 with a five-set win over fourth seed Alexander Zverev on Saturday.
Ranked 58, Chung finished strongly to oust the German 5-7, 7-6, 2-6, 6-3, 6-0 in 3hr 22min on Rod Laver Arena and will face either Novak Djokovic or Albert Ramos-Vinolas in Monday's fourth round.
Chung's feat also makes him only the third South Korean player - man or woman - to reach the round of 16 at a grand slam tournament.
"It was really tough, he is a really good player and we know how to play each other," said the glasses-wearing 21-year-old player, who trained in the heat of Thailand before coming to Melbourne.
"I played Novak two or three years ago, so if he wins tonight I just want to enjoy things on the court."
Women's action on Day 6: Halep and Pliskova show mettle in the third round
Matches to watch on Day 6: Maria Sharapova faces Angelique Kerber hurdle
Roger Federer defends Aus Open organisers: 'You've got to play in all conditions'
Thiem wins in straight sets
Austria's fifth seed Dominic Thiem reached the round of 16 with a straight-sets win over Frenchman Adrian Mannarino on Saturday.
Thiem downed the 26th-seed 6-4, 6-2, 7-5 in 2hr 8min on Margaret Court Arena and will face either German Maxmilian Marterer or American Tennys Sandgren for a place in the quarter-finals.
The Austrian has now reached the round of 16 at his last six grand slam tournaments.
Thiem showed no ill-effects of his five set win over American qualifier Denis Kudla in the second round in fierce heat on Thursday.
The victory took his record over Mannarino to 7-0.
Fognini battles into Round 4
Italy's Fabio Fognini reached the round of 16 for the second time with a five-set victory over Frenchman Julien Benneteau Saturday.
Fognini, seeded 25, downed the 59th-ranked Benneteau 3-6, 6-2, 6-1, 4-6, 6-3 in three hours on Hisense Arena.
He will play either Argentine 12th seed Juan Martin Del Potro or Czech 19th seed Tomas Berdych in Monday's fourth round.
The victory equalled 30-year-old Fognini's best result at the Australian Open. His best Grand Slam showing was the quarter-finals at Roland Garros in 2011.