Kristina Mladenovic beat defending champion Roberta Vinci to reach the semi-final of the St Petersburg Ladies Trophy after top seed Simona Halep's tournament was cut short due to injury on Friday.

Vinci must have fancied her chances of winning in Russia this weekend after Halep was forced to withdraw from her quarter-final against Natalia Vikhlyantseva due to a knee problem.

But the Italian was sent packing by the unseeded Mladenovic, who followed up her second-round win over Australian Open runner-up Venus Williams by prevailing 6-1 6-4.

Mladenovic will face Russian outsider Vikhlyantseva in the last four after setting about the Vinci serve in a one-sided first set and claiming the only break of the second when her experienced opponent double-faulted to go 5-4 down.

The world number 51 from France served out the match to stand just two victories away from a maiden WTA singles title.

However, Dominika Cibulkova is the favourite to succeed Vinci as champion after ousting Elena Vesnina 6-3 6-3.

Vesnina's hopes of taking the title in her homeland were ended by the second seed, who broke three times in each set to set up a meeting with the unseeded Yulia Putintseva.

It is left for Vikhlyantseva to fly the flag for Russia after Putintseva claimed the scalp of the Svetlana Kuznetsova, seeing off the third seed 6-3 6-7 (4-7) 7-5 to reach her first WTA Premier semi-final.