PARIS — World No. 1 Naomi Osaka was just two points from a sensational Roland Garros exit on Tuesday before securing her place in the second round where she was joined by defending champion Simona Halep who also needed three sets to survive.

Top seed Osaka, bidding to add the French Open to her US and Australian Open titles, defeated Slovakia's Anna Karolina Schmiedlova 0-6, 7-6 (7-4), 6-1.

However, she came within a whisker of becoming only the second top seed to lose in the first round in Paris in the modern era after Angelique Kerber in 2017.

"I think this is the most nervous I have ever been my entire life during a match," said Osaka.

She was also totting up the reasons why she was so under-powered. "First time playing a Grand Slam as No. 1. I have won the last two, so I kind of want to win this one really bad.

"Also I have never played on the Chatrier court before. This was my first time. And, yeah, I kind of feel like I'm having the thought of wanting to prove myself again, so..."

World No. 90 Schmiedlova, who hadn't won a match at the tournament since 2014, twice served for victory in the 10th and 12th games of the second set.

At one stage, she was just two points away from a famous victory. "It hurts that I lost so many chances," said Schmiedlova. "She's the No. 1, it was not easy in my head."

Osaka, who had arrived in Paris still feeling the effects of a hand injury suffered in Rome, raced through the final set and will face former world No. 1 and two-time major winner Victoria Azarenka.

Osaka ended the match with 10 aces, 36 winners and 38 unforced errors — just four of those coming in the decider.

Azarenka, a semifinalist in 2013, reached the second round for the first time since 2015 with a 6-4, 7-6 (7-4) win over 2017 champion Jelena Ostapenko. Third seed Halep overcame a second-set blip against Australian Ajla Tomljanovic to win 6-2, 3-6, 6-1.

Halep, who won her maiden Grand Slam title in Paris last year after three previous final defeats, will next face Poland's Magda Linette.

"The level of the match was great and her level in the second set was really high," said Halep. "So I tried to make her move more and that was better for me. There were nice emotions to be back on this court."

German fifth seed Alexander Zverev, a quarterfinalist in 2018, battled past Australia's John Millman 7-6 (7-4), 6-3, 2-6, 6-7 (5-7), 6-3 in a shade over four hours.

The champion in Geneva last weekend fired 57 winners past world No. 56 Millman who stunned Roger Federer at the US Open last year. However, he also committed 73 unforced errors on a blustery day in the French capital.

"John is a tough player so I knew it would be difficult today," said Zverev, bidding to become the first German man to win the Roland Garros title since Henner Henkel in 1937.

Next up for Zverev is Swedish qualifier Mikael Ymer, the world No. 148 of Ethiopian origin, who marked his Grand Slam debut with a 6-0, 6-3, 7-6 (7-5) win over Slovenia's Blaz Rola.

Argentine eighth seed Juan Martin del Potro, a semifinalist in 2009 and 2018, made the second round with a 3-6, 6-2, 6-1, 6-4 win over Chilean world No. 58 Nicolas Jarry.

"I think I'm playing well at the moment, but my main goal is still the knee, my health," said Del Potro who is still feeling his way back after knee surgery. Next up for the giant Argentine is a clash against Japan's Yoshihito Nishioka, who beat American Mackenzie McDonald 6-7 (7-9), 6-0, 4-6, 6-2, 6-3.

Russian 10th seed Karen Khachanov eased past Cedrik-Marcel Stebe 6-1, 6-1, 6-4. Joining him in the second round was Frenchman Lucas Pouille, the 22nd seed, who defeated Simone Bolelli 6-3, 6-4, 7-5.

Italian Fabio Fognini, one of the players tipped to do well in Paris after defeating Rafa Nadal en route to the Monte Carlo title last month, beat compatriot and doubles partner Andreas Seppi 6-3, 6-0, 3-6, 6-3.

Kyle Edmund completed a 7-6(7-1), 5-7, 6-4, 4-6, 7-5 victory over Frenchman Jeremy Chardy in a match that resumed on Tuesday after bad light stopped play on Monday. Fellow Briton Cameron Norrie fell 6-3, 6-0, 6-2, to local qualifier Elliot Benchetrit.

Ivo Karlovic made a mockery of his 40 years to beat relative spring chicken, 37-year-old Feliciano Lopez, in the oldest ever men's match-up at Roland Garros.

Croatian Karlovic, the tallest player on the tour at 6ft 11in (2.11m), defeated Lopez 7-6 (7-4), 7-5, 6-7 (7-9), 7-5. He is the oldest man to win a Grand Slam match since Ken Rosewall in 1978.

Canada's Bianca Andreescu, the surprise champion at Indian Wells, marked her Roland Garros debut by beating Marie Bouzkova of the Czech Republic 5-7, 6-4, 6-4.

The 18-year-old, playing for the first time since Miami after suffering a shoulder injury, hit 58 winners and 60 unforced errors.

Andreescu salvaged Canada's French Open hopes as she came through a tough opening test. Canadian Tennis has been on a high with the rise of Andreescu, fellow teenager Felix Auger Aliassime and 21-year-old Denis Shapovalov, but 22nd seed Andreescu is the only one of the trio to reach round two.

Auger Aliassime withdrew injured while Shapovalov lost on Monday. Former Wimbledon runner-up Milos Raonic is injured. Andreescu missed the claycourt season to rest her injured shoulder, opting to practice in Mallorca.

Andreescu will play American Sofia Kenin next. There was no joy for Canada's former golden girl Eugenie Bouchard, who went down 6-2, 6-2 to Ukraine's Lesia Tsurenko. — Agencies

American Madison Keys, the 2018 sem-finalist, beat Evgeniya Rodina 6-1, 6-2 to set up a second round meeting with Australian wild card Priscilla Hon.