Wimbledon champion Petra Kvitova has won the WTA Championships in Istanbul with a three-set victory over Victoria Azarenka.

World number four Azarenka raced in a 5-0 lead in the opening set, only for 21-year-old Kvitova to reply with seven straight games to claim the first set.

Azarenka responded by breaking early in the second set, before going on to record a 6-4 success to level up the match.

Kvitova, 21, controlled the deciding set and served for the title to record a 7-5 4-6 6-3 triumph at the end of season finale.