MELBOURNE (AFP) - A focused Serena Williams sent an ominous Australian Open warning with a 49-minute first-round demolition on Tuesday (Jan 15), as young gun Alexander Zverev comfortably began his tilt at a maiden Grand Slam title.

The American giant is bidding to match Margaret Court's record of 24 Grand Slam singles crowns on her first return to Melbourne Park since winning in 2017 while eight weeks pregnant.

Now 37, she kept a low profile in the lead-up to the opening major of the year and came out of the blocks flying against fellow mum Tatjana Maria, pummelling her German opponent 6-0, 6-2.

Sporting a striking jade green jumpsuit and fine mesh stockings on Rod Laver Arena, the 16th seed wasted no time in getting out of the blistering Melbourne heat and said it was good to be back.

"The last time I was here I was pregnant and playing at the same time which is insane," she said. "It's weird walking back on - by myself this time - it feels good. I have so many memories from last time I was here."

Bidding for an eighth Melbourne Park singles crown and 13th in total, few are betting against her despite her lowly seeding and she next faces Canadian Eugenie Bouchard, who eased past China's Peng Shuai.

Williams played at the mixed-team Hopman Cup in Perth this month, winning all three matches but her appearance on Tuesday was her first outing on tour since a meltdown in losing the US Open final to Naomi Osaka in September.

The fourth-seeded Japanese begins her campaign in the night match on Rod Laver Arena against Poland's Magda Linette following Novak Djokovic's first outing.

Czech seventh seed Karolina Pliskova, who has made the quarter-finals in her last two appearances at Melbourne Park, safely progressed as did Williams' 38-year-old sister Venus, who incredibly played her first Grand Slam tournament 22 years ago. Unseeded, she booked a place in round two by beating 25th seed Mihaela Buzarnescu over three tough sets.

But 10th seed Darya Kasatkina slumped out, winning just three games against Switzerland's Timea Bacsinszky.

American Madison Keys, who reached the semis at the French and US Open last year, as well as the quarters in Melbourne, ensured she too lived to fight another day, crushing local wildcard Destanee Aiava 6-2, 6-2.

Last year's beaten finalist and world No. 1 Simona Halep plays Kaia Kanepi later.

However, it is the end for former world No. 1 and two-time champion Victoria Azarenka, who threw away a one-set lead against Laura Siegemund.

The Belarusian, who has tumbled down the rankings since the birth of son Leo and a messy custody battle afterwards, slumped out 6-7 (5-7), 6-4, 6-2 to the German.

Like Williams, men's world No. 1 Djokovic is also gunning for a piece of history as he looks to win a record seventh Australian Open title.

The Serb starts against American qualifier Mitchell Krueger.

Zverev does 'everything right'

Fourth seed Zverev, who is looking to win his first Slam title and establish himself as a serious threat to Djokovic, Roger Federer and Rafael Nadal, cruised past Aljaz Bedene 6-4, 6-1, 6-4.

"I've had about 86 injuries and the ankle is still a bit swollen," said the 21-year-old.

"But I've done everything right in my preparation. Now I either play well or I don't."

Eighth seed Kei Nishikori, who won in Brisbane last week, looked down and out against little known qualifier Kamil Majchrzak, losing the first two sets before the Pole began badly cramping.

He bravely fought on before calling it a day after winning just two of the next 17 games.

"I was trying to play but he was playing amazing tennis. I have to be happy that I didn't lose today," said a relieved Nishikori, who next faces Croat Ivo Karlovic.

Elsewhere, 15th seeded Russian Daniil Medvedev went through in three sets, while 12th seeded Italian Fabio Fognini beat Spain's Jaume Munar, who retired with cramps while two sets down.

South Korea's Chung Hyeon, a giant-killer last year when he beat Zverev and Djokovic on the way to the semi-finals, demonstrated his fighting qualities again, coming from two sets down to beat American Bradley Klahn.

In other matches on Tuesday, Australian hero Nick Kyrgios will have his work cut out against Canadian 16th seed Milos Raonic, a former world No. 3.