It came on a day of five-set tests for a trio of top players in round two of the men's draw at Roland Garros.

Romania's Halep, last year's beaten finalist who has still never won a Grand Slam title, lost the first-set 6-2 against American opponent Alison Riske before bouncing back to win the next two 6-1, 6-0.

There was easier progress for second seed and Australian Open winner Caroline Wozniacki, as the Dane cruised past Spain's Georgina Garcia Perez 6-1, 6-0, while Ukraine's fourth seed Elina Svitolina beat Slovakia's Viktoria Kuzmova 6-3, 6-4. 

Czech Republic's eighth seed Petra Kvitova, a two-time Wimbledon champion, also beat a Spanish opponent in Lara Arruabarrena, 6-0, 6-4.

In the men's draw, Germany's second seed Alexander Zverev was among those stretched today in a 2-6, 7-5, 4-6, 6-1, 6-2 win over Serbia's world number 60 Dusan Lajovic.

Bulgaria's fourth seed Grigor Dimitrov was similarly stretched before winning 6-7, 6-4, 4-6, 6-4, 10-8 against US opponent Jared Donaldson in a match lasting over four hours.

Japan's Kei Nishikori continued his return to Grand Slam action following injury with a topsy-turvy 6-3, 2-6, 4-6, 6-2, 6-3 win over France's Benoit Paire.

But Marco Trungelliti, the Argentinian "lucky loser" who drove from Barcelona to take up his last-minute place before beating Australia's Bernard Tomic, was beaten 6-1, 7-6, 6-1 today by Marco Cecchinato of Italy.

Action on the clay in Paris will continue tomorrow.