Australian Open contenders Novak Djokovic, Roger Federer, Serena Williams, Ash Barty and Naomi Osaka all recorded good wins to reach the third round at Melbourne Park.
Naomi Osaka Photo: PHOTOSPORT
Defending champion Djokovic made quick work of Japan's Tatsuma Ito with a comfortable 6-1 6-4 6-2 victory, while 20-times Grand Slam winner Federer beat Filip Krajinovic of Serbia 6-1 6-4 6-1.
Third seed Roger Federer, chasing a record-extending 21st Grand Slam title reached the third round at Melbourne Park for the 21st straight year.
Federer came into the year's first Grand Slam without playing any warm-up events but has dropped only 13 games in two matches to reach the third round.
In the women's draw, Serena Williams, who is bidding for a record-equalling 24th Grand Slam singles title, eased past Slovenian Tamara Zidansek 6-2 6-3.
Defending champion Naomi Osaka said after her win over Zheng Saisai that she was not giving too much thought to reclaiming the world number one ranking, with top-ranked Ash Barty well in front of the Japanese third seed.
Barty looked in ominous form in her quest for a second Grand Slam title as she powered past unseeded Slovenian Polona Hercog 6-1 6-4.
Defending champion Naomi Osaka fended off a strong comeback attempt from China's Zheng Saisai, rallying from 4-2 down in the second set to prevail 6-2 6-4 and reach the third round.
American teenage sensation Coco Gauff rallied from a set down to beat Sorana Cirstea 4-6 6-3 7-5 in a thrilling encounter.
Novak Djokovic Photo: PHOTOSPORT
The 15-year-old Gauff, who beat seven-time Grand Slam champion Venus Williams in the opening round, will face defending champion Naomi Osaka in the last 32.
Unseeded American Tommy Paul ended Bulgarian 18th seed Grigor Dimitrov's hopes of capturing his first Grand Slam title as the world number 80 won 6-4 7-6(6) 3-6 6-7(3) 7-6(3) in four hours and 19 minutes.
Meanwhile two of the three New Zealanders advanced in the first round of men's doubles.
Michael Venus and Artem Sitak are both through to the second round but Marcus Daniell has bowed out of the tournament.
7th seeds Venus and Australian John Peers bounced back from the disappointment of losing in the first round of the ASB Classic by beating Dane Freddie Nielsen and Germany's Tim Puetz 7-5 6-3 in 1 hour 14.
Venus and Klaasen will play the Argentine pair of Federico Delbonis and Leonardo Mayer in the second round.
Artem Sitak and his Indian partner Divij Sharan overcame the dangerous pair of Portugal's Joao Sousa and Spain's Pablo Carreno Busta 6-4 7-5 in 1 hour and 28 minutes.
Sitak and Sharan will play either ASB Classic champions Ben McLachlan and Luke Bambridge or 10th seeds Mate Pavic and Bruno Soares in the second round.
The third Kiwi in the draw Marcus Daniell and his Austrian partner Philipp Oswald were beaten 6-4 6-4 by 6th seeds Marcel Granollers and Horacio Zeballos.
Reuters/RNZ