Top seeds Karolina Pliskova and Angelique Kerber strolled to straight-sets wins in the first round of the Internationaux de Strasbourg, keeping the two former world number ones on course for a final meeting.

Having endured an injury-hit season to date, world number eight Pliskova made the perfect start to her campaign in France with a routine 6-4 6-2 win over Ukrainian 19-year-old Marta Kostyuk. 

Kerber, who is only missing a victory at the French Open – which begins later this month – to complete a Career Grand Slam, overcame teenager Diane Parry 6-3 6-4 in her opener, setting up a round-of-16 clash with world number 45 Aliaksandra Sasnovich.

Some of the other big names participating in Strasbourg, however, were not so lucky, with 5th and 6th seeds Shuai Zhang and Sloane Stephens crashing to first-round exits.

Shuai went down 6-2 6-3 to Belgium's Maryna Zanevska and Stephens capitulated to a 2-6 6-4 6-1 loss to Nefisa Berberovic, while Heather Watson set up a last-16 meeting with eighth seed Magda Linette by beating Katharina Hobgarski 6-4 6-1.

Meanwhile, Garbine Muguruza made a winning start to her campaign at the Grand Prix Sar La Princesse Lalla Meryem in Morocco, as the world number 10 builds towards a tilt at French Open glory having triumphed at Roland Garros back in 2016.

Muguruza had few difficulties in beating Anna Danilina 6-3 6-2, and will face Martina Trevisan in the round-of-16 after the Italian beat China's You Xiadoi 6-0 6-4.

Third seed Nuria Parrizas-Diaz had to come through a more difficult challenge in Rabat, overcoming Carol Zhao 7-6 (7-4) 1-6 6-2, while eighth seed Anna Kalinskaya was the highest-ranked player to fall at the first hurdle, going down 6-3 6-7 (5-7) 6-3 to Lucia Bronzetti.