Anna Kournikova stunned world number one Martina Hingis 63, 7-6 (7/1) yesterday to advance to the semi-finals of the German Open.

It was the Russian youngster's first victory over Hingis in five meetings, and Hingis's fourth defeat this year. She had already lost twice to Venus Williams, in Sydney and Key Biscayne, and gone down to Lindsay Davenport in Tokyo.

The 16-year-old Russian will now face seventh-seeded Conchita Martinez after the Spaniard overcame 16th seed Ai Sugiyama of Japan 6-3, 6-3.

In the other semi-final, third seed Jana Novotna of the Czech Republic takes on French qualifier Amelie Mauresmo. Novotna rallied to beat eighth-seeded Romanian Irina Spirlea 6-3, 5-7, 6-3, while Mauresmo overcame Barbara Paulus of Austria 6-4, 6-2.

Hingis was clearly tired after a recent campaign that has seen her win titles in both Hamburg and Rome. She was lethargic and made far more unforced errors than Kournikova, especially in over-hitting the ball. Her serve was also vulnerable, and was often punished with a winning return.

In contrast, Kournikova looked eager and was very aggressive. Her double-handed backhand, hit both down the line and cross court, was especially impressive.

Whenever Hingis hit short, Kournikova was quick to the net to volley a winner, and she was equally competent from the baseline. Hingis gained the glimmer of a chance when Kournikova failed to convert three match points at 5-3, with two of the opportunities lost on nervous backhand errors.

Hingis also held two break points for 6-5, but Kournikova remained composed and weathered the storm, and then surrendered just one point in the tie-break.

"You don't have every day match points against the number one player," said 14th seed Kournikova.