Highlights: French Open day eight

(Reuters) - Top seed Simona Halep and fifth seed Kiki Bertens suffered shock fourth-round defeats at the French Open on Sunday, while Alexander Zverev revealed he played with fever and breathing difficulties following his loss to Italian Jannik Sinner.

Halep, a heavy favourite to lift a second title at Roland Garros, was stunned 6-1 6-2 by Polish teenager Iga Swiatek, who moved into a Grand Slam quarter-final for the first time.

Swiatek will next face Italian qualifier Martina Trevisan who secured a hard-fought 6-4 6-4 win over Dutchwoman Bertens.

Losses for Halep and Bertens mean there are only four seeded players remaining in the women's singles draw - Elina Svitolina, Sofia Kenin, Petra Kvitova and Ons Jabeur.

Sixth seed Zverev was seen coughing on court and admitted he "should not have played" after a 6-3 6-3 4-6 6-3 defeat by teenager Sinner.

The French Tennis Federation (FFT), which runs the claycourt Grand Slam, told Reuters that Zverev last tested for COVID-19 on Sept. 29 and the test returned a negative result the following day.

Twelve-times champion Rafa Nadal raced into another quarter-final with a 6-1 6-1 6-2 victory over American qualifier Sebastian Korda.

U.S. Open champion Dominic Thiem survived a scare as he edged out French wildcard Hugo Gaston 6-4 6-4 5-7 3-6 6-3.

Highlights of the eighth day at the French Open, the final Grand Slam tournament of the year, on Sunday (all times GMT):

1820 THIEM SURVIVES GASTON SCARE

U.S. Open champion Dominic Thiem overcame a spirited challenge from French wildcard Hugo Gaston to secure a 6-4 6-4 5-7 3-6 6-3 win in just over 3-1/2 hours.

Third seed Thiem extended his winning streak against French opponents at Grand Slams to 10 matches.

1415 PODOROSKA SEALS COMEBACK WIN

Argentine qualifier Nadia Podoroska rallied from a set down to beat Czech Barbora Krejcikova 2-6 6-2 6-3.

1410 SINNER STUNS ZVEREV TO SET UP NADAL CLASH

Italian teenager Jannik Sinner struck 39 winners as he produced a shock 6-3 6-3 4-6 6-3 win over Germany's sixth seed Alexander Zverev.

Sinner, playing in his first Roland Garros main draw, will next face 12-times champion Rafa Nadal.

1400 SVITOLINA EASES INTO QUARTERS

Third seed Elina Svitolina broke local favourite Caroline Garcia's serve six times en route to a comfortable 6-1 6-3 win.

1235 NADAL BREEZES INTO ANOTHER QUARTER-FINAL

Defending champion Rafa Nadal faced little resistance from American qualifier Sebastian Korda as the Spaniard claimed a 6-1 6-1 6-2 win in just under two hours.

Nadal has reached the Roland Garros quarter-finals without dropping a set for the eighth time.

1050 TOP SEEDS HALEP, BERTENS KNOCKED OUT IN STRAIGHT SETS

Polish teenager Iga Swiatek caused a stunning upset when she beat top seed Simona Halep in straight sets to win 6-1 6-2 on court Philippe Chatrier to advance to the quarter-finals.

Meanwhile, fifth seed Kiki Bertens also exited in the last-16 after Italian qualifier Martina Trevisan won 6-4 6-4 with 22 winners and 18 points at the net.

0915 PLAY UNDER WAY AT ROLAND GARROS

Play got underway at Roland Garros in cloudy conditions with the temperature hovering around 11 degrees Celsius (51.8°F).

Top seed Simona Halep is taking on Polish teenager Iga Swiatek under the roof on court Philippe Chatrier.

Defending champion Rafa Nadal is in action later when he faces American Sebastian Korda.

(Reporting by Rohith Nair and Hardik Vyas in Bengaluru; Editing by Toby Chopra and Toby Davis)