Defending champion Elena Rybakina and world number two Aryna Sabalenka began their Wimbledon preparations with wins as the grass-court season continues.

Sabalenka also began strongly with a 6-3 6-2 win over Russia's Vera Zvonareva.

Meanwhile, last year's winner Ons Jabeur started her grass-court season with a 7-6 (7-4) 6-4 defeat by German qualifier Jule Niemeier.

The Tunisian fourth seed, who was runner-up at Wimbledon last year, has struggled with injury since the start of the year and squandered two set points in the opening set to fall at the first hurdle of her title defence.

Ranked 120th in the world, Niemeier made the quarter-finals of Wimbledon last year and will face 2019 US Open champion Bianca Andreescu or 2019 Roland Garros runner-up Marketa Vondrousova in the next round.

Kazakhstan's Rybakina pulled out of the French Open through illness but looked in fine form in her first grass-court tournament to set up a last-16 tie against Croatia's Donna Vekic as she warms up for her Wimbledon title defence with the tournament beginning on 3 July.

Australian Open champion Sabalenka did not compete at last year's Wimbledon following the All England Club's ban on Russian and Belarusian players competing because of Russia's invasion of Ukraine.

She was critical of that decision, saying it achieved "nothing", but added that "no-one supports war" and said she did not watch the Championships last year.

However, the 25-year-old top seed secured a comprehensive win over veteran Zvonareva in just 66 minutes and will face Russian Veronika Kudermetova or China's Zheng Qinwen in the next round.

American fifth seed Coco Gauff also secured a 6-3 6-4 win over the Czech Republic's Katerina Siniakova, and should she and Sabalenka progress they will meet in the quarter-finals.

Zverev beats Thiem in Halle

At the Halle Open, German world number 22 Alexander Zverev beat Dominic Thiem in a rematch of the 2020 US Open final, which Thiem won in dramatic fashion.

It was both men's first grass-court match since 2021 and, following a third consecutive semi-final appearance at the French Open, Zverev beat the Austrian 6-3 6-4 in front of a home crowd and will face Canadian Denis Shapovalov in the next round.

Thiem, ranked 89 in the world, has been knocked out in the first round of three of his past four tournaments.

Elsewhere, Italy's Jannik Sinner, a quarter-finalist at Wimbledon last year, beat France's Richard Gasquet 6-3 5-7 6-2 to progress.

Russian third seed Andrey Rublev beat China's Wu Yibing 6-4 6-7 (5-7) 6-2 and will face German wildcard Yannick Hanfmann next.