Former champion Simona Halep suffered a mid-match panic attack as the Romanian lost her second-round match at the French Open.

Halep, the 2018 winner, was another big name to be knocked out on a day that produced more upsets at Roland Garros.

But world number one Iga Swiatek overwhelmed another opponent in Paris.

Swiatek, 20, is one of only three remaining top-10 seeds in the women's singles draw after the opening two rounds, along with Spanish third seed Paula Badosa and seventh seed Aryna Sabalenka from Belarus.

Halep struggled physically in the second half of her match against her 19-year-old opponent, fading badly in the second set as Zheng won 11 of the final 12 games.

Two-time Grand Slam champion Halep had led by a set and a break but said she "didn't know how to handle" the situation when a rare panic attack took hold.

"I don't have it often," Halep said. "I don't really know why it happened, because I was leading the match. I was playing well.

"But it just happened and as I said, I lost it. I couldn't focus," she added.

"After the match was pretty tough but now I'm good. I'm recovered and I will learn from this episode.

"[It was] nothing dangerous, in my opinion, but it happened. So it's good that now I can smile."

Halep's exit was the latest high-profile defeat in the women's draw.

The upset of the day came against Wimbledon runner-up Karolina Pliskova, who was stunned 6-2 6-2 by French world number 227 Leolia Jeanjean.

Ninth seed Danielle Collins was another seed to fall on Thursday as she lost 6-4 6-3 to fellow American Shelby Rogers.

Can anyone stop Swiatek at Roland Garros?

There were no such problems for Swiatek, though, and the question of who is potentially going to stop the top seed at the French Open is being asked louder with each passing day.

On Thursday, the 2020 champion overwhelmed another opponent with a rapid win to cruise into the third round at Roland Garros.

Swiatek needed just 61 minutes to clinch a 6-0 6-2 win against American Alison Riske.

After a 54-minute win over Ukraine's Lesia Tsurenko in her opener, Swiatek has now won her past 30 matches and is aiming for a sixth successive title.

"I feel like I'm using my new position to put more pressure on my opponents," said Swiatek, who became world number one in March after Ashleigh Barty's shock retirement.

"I'm pretty happy that I could convert it to a way that is really helpful. I feel like my confidence is better."

Swiatek has come into the clay-court Grand Slam as the biggest favourite for a women's major title in recent times following a stunning run in which she has dominated the WTA Tour.

"I'm pretty happy. I'm playing solid tennis," said Swiatek, winner of titles in Doha, Indian Wells, Miami, Stuttgart and Rome this year.

"I'm a perfectionist so I can still work on lots of things."

The power and accuracy of her groundstrokes, particularly from the forehand, have proved difficult for anyone recently to cope with. Riske, ranked 43rd, was the latest opponent to have few answers.

One of the hallmarks of Swiatek's success has been her ruthlessness and a 20-minute first set was the 15th bagel - a tour high - she had inflicted this year.

Seven points were all she allowed Riske and the dominance continued at the start of the second set.

After another ball flew past, the American simply shrugged at her box as if to say 'What can I do?'.

The unstoppable winners from Swiatek continued, although she showed she was human - hitting a volley into the net - to enable Riske to finally get on the board after 42 minutes.

A broad smile broke across Riske's face as the crowd on Court Suzanne Lenglen showed their support with a hearty round of applause.

That was about as fun as it got for Riske, with Swiatek going on to clinch a straightforward win which means she is only the fourth WTA player this century to win 30 matches in a row.

"I know how many matches I have won in a row, because you keep reminding me, basically," Swiatek, who plays Montenegro's Danka Kovinic next, joked to reporters.

"But I don't keep track. I'm not like noting them."

Spain's Badosa, who won the Indian Wells title in October, is the second highest seed left following defending champion Barbora Krejcikova's first-round defeat.

A quarter-finalist last year, the 24-year-old moved into the third round with a 7-5 3-6 6-2 success against Slovenia's Kaja Juvan.

Meanwhile, Sabalenka required just over an hour to despatch American Madison Brengle 6-1 6-3.

But 2017 winner Jelena Ostapenko, Latvia's 13th seed, was beaten 6-0 1-6 6-3 by France's Alize Cornet, who was roared on by the Court Philippe Chatrier crowd during Thursday's night session.

Eleventh seed Jessica Pegula won 6-1 5-7 6-4 against Anhelina Kalinina of Ukraine, while Madison Keys was another American to triumph, defeating France's Caroline Garcia 6-4 7-6 (7-3).

Italy's Camila Giorgi and Russian Veronika Kudermetova, seeded 28th and 29th respectively, also won their matches.

Giorgi gained a 6-3 7-5 victory against Yulia Putintseva of Kazakhstan, while Kudermetova triumphed 6-3 6-3 in her match with Aleksandra Krunic of Serbia.