PARIS - World No 1 Naomi Osaka found herself on the brink of elimination but managed a full-set victory over Anna Karolina Schmiedlova, while China's Wang Qiang got past compatriot Zheng Saisai in straight sets in the women's singles first round of French Open here on Tuesday.

In her first Grand Slam as the top seed, Osaka recovered from a bagel in the first set to overcome the 90th-ranked Slovakian 0-6, 7-6 (4), 6-1 in a windy condition.

Even in the second set, Schmiedlova got the chance of serving out the match twice, but it turned out that Osaka marched on.

"This is the most nervous I have ever been my entire life during a match. You could see that in the first set. I was literally not hitting any balls on the court," Osaka explained.

Osaka set up a second round encounter with Victoria Azarenka. The former world No 1 dispatched the 2017 titlist Jelena Ostapenko 6-4, 7-6 (4).

"The opponent for the first round was one of the toughest in the draw. I was rushing too much, and conditions were very tough. It was super windy today," Ostapenko admitted after her first-round exit for the second year running.

Azarenka said, "I love to challenge myself against the best players. I had some good wins in the last couple of weeks against top 10 players, so I feel that I'm ready to play against top players."

Joining top seed in the second round was the reigning champion Simona Halep, who triumphed over Ajla Tomljanovic of Australia 6-2, 3-6, 6-1.

Zheng easily conceded the first set 6-1 despite managing a break in the fifth game, before making adjustment in the followed-up set to stay ahead at 5-4. Then Wang steadied her nerves to bag three games in a row and secure her win with a precise backhand.

Another Chinese player Zhu Lin failed in her maiden Roland Garros main draw appearance with a 6-1, 6-1 loss to Romania's Irina-Camelia Begu.

Following three consecutive five-set thrillers en route to quarterfinals last year, men's singles fifth-seeded Alexander Zverev nailed another marathon victory over John Millman of Australia 7-6 (4), 6-3, 2-6, 6-7 (5), 6-3.

"Very difficult to play today. But it's great that I came through, and this is the most important," Zverev pointed out.

No 8 seed Juan Martin del Potro shrugged off a sluggish start to see off Nicolas Jarry 3-6, 6-2, 6-1, 6-4.

He was followed by Fabio Fognini, as the ninth seed eliminated his fellow Italian Andreas Seppi 6-3, 6-0, 3-6, 6-3.

No 10 seed Karen Khachanov and local favorite Gael Monfils also reached the second round in straight sets.

The 11-time winner Rafael Nadal and Swiss veteran Roger Federer headline Wednesday's second round in men's singles.

China's Zhang Shuai will meet Estonian veteran Kaia Kanepi in the women's singles second round, before partnering Austrailian John Peers for mixed doubles opener.

Zheng Saisai hopes to make some redemption with Duan Yingying in the women's doubles action, also featuring Han Xinyun/Wang Yafan on Wednesday.