Serena Williams and Naomi Osaka wasted little time in breezing into the second round as the Australian Open began on Monday, three weeks later than originally scheduled because of the coronavirus pandemic.

Japan's Osaka, the third seed, struck the first serve on Rod Laver Arena against Russia's Anastasia Pavlyuchenkova in the women's singles and strode to touch racquets with her opponent at the net just 68 minutes later after a 6-1, 6-2 victory.

"I was really nervous coming into this match. I just wanted to play well," Osaka told a smattering of spectators on the socially-distanced centre court. She will face France's Caroline Garcia in the second round.

Williams started her quest for a record-equalling 24th Grand Slam title in style with a 6-1, 6-1 romp past Germany's Laura Siegemund in 56 minutes.

"This was a good start, it was vintage Serena," said the 39-year-old, playing an unparallelled 100th match at the tournament and turning heads by sporting a vivid, one-legged catsuit.

She will play Serbia's Nina Stojanovic in the second round. But 2016 Australian Open champion Angelique Kerber was the first significant casualty, the 23rd-seeded German losing 6-0, 6-4 to 63rd-ranked American Bernada Pera on Margaret Court Arena.

The tournament is known as the "Happy Slam" for its convivial atmosphere but the pandemic has overshadowed the event this year with fewer spectators, mandatory mask-wearing and fans unable to circulate freely around the grounds.

Australia has largely contained the virus, but officials are desperate to avoid further problems from Covid-19.

Wawrinka through

Preparations had to be hastily rearranged as late as last Wednesday when a coronavirus case at a tournament hotel -- the city's first local infection in 28 days -- forced a suspension of play.

Hundreds of players and officials were tested and all were negative. While Kerber exited early, there were no problems for the 2014 men's champion, Stan Wawrinka, as he reached the second round for a 16th straight time with a 6-3, 6-2, 6-4 win against Portugal's Paulo Sousa.

"It's always amazing and special to come back here. Winning my first Grand Slam was something unbelievable, amazing memories," said the 35-year-old Swiss 17th seed.

Milos Raonic, the 14th seed from Canada also enjoyed serene progress through to the second round with a 6-3, 6-3, 6-2 win over Federico Coria of Argentina.

But Gael Monfils, the French 10th seed, is out after being stunned 3-6, 6-4, 7-5, 3-6, 6-3 by Emil Ruusuvuori of Finland, the world number 86, in three hours and 46 minutes.

Raonic -- who reached the semi-final at Melbourne Park in 2016 and the last eight a year ago, before losing to eventual champion Novak Djokovic -- next plays Corentin Moutet of France.

Men's number one Djokovic, looking for a record-extending ninth Melbourne Park crown, begins his quest later Monday in the late night match on Rod Laver Arena against France's Jeremy Chardy.

Women's world number two Simona Halep, who has been battling a back injury which hampered her preparations, will open the evening session against Australian wild card Lizette Cabrera.

Top women's seed Ashleigh Barty, defending champion Sofia Kenin and 20-time men's singles Grand Slam champion Rafael Nadal all to begin their challenge for this year's Australian Open on Tuesday's second day.