World number one Angelique Kerber and Slovakia’s seventh seed Dominika Cibulkova secured semi-final places at the WTA Finals as both players won their final group matches in Singapore.

Kerber beat American Madison Keys 6-3 6-3 to claim her third win of the week.

Cibulkova had required the German to win in straight sets to progress from the White Group, having earlier beaten Romania’s Simona Halep 6-3 7-6 (7-5).

Russia’s Svetlana Kuznetsova had already qualified from the Red Group.

Kuznetsova, who only qualified for the season-ending event last Saturday, will play Cibulkova in the last four, while Kerber will face the winner of Friday’s final round-robin match between Poland’s defending champion Agnieszka Radwanska and Czech fourth seed Karolina Pliskova.

Cibulkova’s straight-set victory guaranteed Kerber’s place in the semi-finals, and the Slovak then had to wait and hope that Kerber would return the favour with a two-set win over Keys.

“Probably I’ll be checking the score, but that’s the worst thing you can do,” Cibulkova said after her match.