Organisers cancelled five singles matches as persistent rain washed out a large chunk of play on the opening day of the Australian Open on Sunday, disappointing the large crowds who had flocked to Melbourne Park.

Olympic champion Zheng Qinwen, teenager Mirra Andreeva, Donna Vekic and Arthur Fils all reached the second round after matches played on the three showcourts which have roofs, but less than an hour's play was possible outside by early evening.

Five of the 32 scheduled singles matches were scratched and organisers will be giving thanks for the cushion of the extra day which was first added to the tournament last year.

The mood and weather had been far brighter at the start of the day as fans formed lengthy queues at the gates eager for the start of the biggest sporting event of the Australian summer.

The number of matches on the first few days of the tournament mean that tennis enthusiasts can watch main draw singles action on the outer courts for the relatively cheap price of a ground pass.

They were sent scurrying for cover inside the first hour of play, however, when a violent storm swept across the precinct accompanied by flashes of lightning and explosive cracks of thunder.

"Lovely time here, beautiful sitting in the arena, nice watching the water collect, but we didn't get any tennis," said local academic Alex with more than a hint of sarcasm in her voice.

"We've paid 60 bucks and haven't seen anything."

The roofs of the showcourts had already been closed and Chinese number one Zheng and Romanian qualifier Anca Todoni continued their baseline battle on Rod Laver Arena despite the wet weather.

Zheng, who is looking to emulate her idol Li Na's Australian Open triumph of 2014, was always going to attract a lot of support given the number of her compatriots who travel to Melbourne each year.

The 22-year-old's last competitive match on the main showcourt was her loss to Aryna Sabalenka in the 2024 final, and the tall Todoni ensured her return was not as comfortable as she might have hoped.

The fifth seed, who did not play a warm-up tournament, finally broke for 4-3 in the opening set but Todoni toughed it out, battling through four deuces to hold serve before breaking back for 5-5 and earning a set point.

Zheng saved the set point then took the tiebreaker 7-3 and quickly raced to a 3-0 lead in the second set while Todoni, who had treatment on her back, racked up unforced errors as she fought in vain to stay in the contest.

"The first match is never easy and I made some stupid mistakes," Zheng said after wrapping up her 7-6(3) 6-1 win in a shade under two hours.

"There's more and more pressure (on me but) I think deal good with the pressure and, as Billie Jean King said, pressure is the privilege. Let's keep going playing with pressure."

Andreeva was earlier the first player to reach the second round at the 113th edition of the championships when the 17-year-old Russian beat Czech Marie Bouzkova 6-3 6-3 on John Cain Arena.

On Margaret Court Arena, the other court with a roof, Fils was the first player to make it into the men's second round when he came from a set down to beat unseeded Finn Otto Virtanen 3-6 7-6(4) 6-4 6-4.

"It's pretty nice, man. First time in my life I'm playing on a good court," the 20th seed said.

"To be able to play a match and to finish a match with a roof, it's much more easy than to play, to stop with the rain."

Croatian 18th seed Donna Vekic, who won Olympic silver behind Zheng in Paris last year, followed Fils onto Margaret Court Arena and beat France's Diane Parry 6-4 6-4.

Women's favourite Sabalenka begins her quest for a third straight title against 2017 U.S. Open champion Sloane Stephens in the opening match of the evening session on Rod Laver Arena. (Reuters)