World number one Iga Swiatek made a winning start at the Australian Open as she beat German Jule Niemeier in straight sets at Melbourne Park.

The Polish 21-year-old will play Colombian Camila Osorio in round two.

There were also victories for third seed Jessica Pegula, sixth seed Maria Sakkari and seventh seed Coco Gauff - who will meet Britain's Emma Raducanu.

Top seed Swiatek, 21, took advantage as Niemeier's serve faltered for the first time to edge the first set.

The German responded with an early break of serve in set two but Swiatek avoided being taken the distance, winning four successive games to set up her meeting with Osario, who beat Hungarian Panna Udvardy 6-4 6-1.

American Pegula swept aside Romania's Jaqueline Cristian 6-0 6-1 in 59 minutes. She will play Aliaksandra Sasnovich next following the Belarusian's 7-5 6-2 win over 15-year-old Czech qualifier Brenda Fruhvirtova.

Sakkari progressed with a 6-1 6-4 win against China's Yue Yuan and moves on to face 18-year-old Russian qualifier Diana Shnaider.

Meanwhile, Gauff defeated Czech Katerina Siniakova 6-1 6-4 to set up an intriguing second-round meeting with Raducanu, who made a positive return to court after her injury scare in a 6-3 6-2 win against Germany's Tamara Korpatsch.

In the battle between the only two former champions in the women's draw, Belarusian two-time winner Victoria Azarenka, whose last triumph in Melbourne came 10 years ago, beat 2020 winner Sofia Kenin of the United States 6-4 7-6 (7-3).

Last year's American runner-up Danielle Collins, seeded 13th, needed three sets to defeat Russian Anna Kalinskaya, eventually winning 7-5 5-7 6-4.

Meanwhile, Wimbledon champion and 22nd seed Elena Rybakina said she "didn't get the benefit which Grand Slam champions normally get" after being scheduled on an outside court for her first-round match.

"But I don't really care and I just want to compete, I want to win. No matter which court I play on, it's great to be here," she said after beating Italian Elisabetta Cocciaretto 7-5 6-3 on court 13.

Rybakina missed out on a chance to break into the world's top 10 when she defeated Ons Jabeur in last summer's Wimbledon final after the ATP and WTA stripped the Grand Slam of ranking points following the organisers' decision to ban Russian and Belarusian players.

Elsewhere, 2019 finalist Petra Kvitova won 7-6 (7-3) 6-2 against Belgian Alison van Uytvanck, while fellow Czech Barbora Krejcikova beat 16-year-old compatriot Sara Bejlek 6-3 6-1.

Canada's 2019 US Open winner Bianca Andreescu beat Czech 25th seed Marie Bouzkova 6-2 6-4, and Latvia's 2017 French Open champion Jelena Ostapenko beat Ukraine's Dayana Yastremska 6-4 6-2.