Dominic Thiem needed a final-set tie-break to reach the semifinals of the St. Petersburg Open at the expense of Daniil Medvedev and Stan Wawrinka saw off defending champion Damir Dzumhur.

Top seed Thiem, in the hunt for a third title of the year, was pushed all the way by home contender Medvedev but sealed a 6-2 3-6 7-6 (7-2) victory.

The world number eight broke three times and served 10 aces as he set up a last-four encounter with Roberto Bautista Agut.

Thiem said: "I'm very sorry that I beat a Russian guy, but I think it was a great match from the beginning until the end. [A] tie-break in a deciding set is always lucky, so I'm lucky that I won."

Wawrinka showed further signs that he is getting back to something like his best with a 6-3 6-4 defeat of 2017 winner Dzumhur.

The three-time grand slam champion won 71 per cent of points on his first serve and broke three times to advance.

Bautista Agut got the better of third seed Marco Cecchinato 7-6 (7-0) 6-3, while Martin Klizan will face Wawrinka after ousting Denis Shapovalov 3-6 7-5 6-3.

Meanwhile, Kei Nishikori moved a step closer to a first tour-level title since 2016 with a 6-3 4-6 6-4 win over Nikoloz Basilashvili in the quarterfinals of the Moselle Open.

Gilles Simon finally came out on top in an all-French encounter with Richard Gasquet in Metz for the first time, winning 7-6 (7-4) 6-2 to end a run of eight consecutive losses against his compatriot and will take on Radu Albot, who beat Ricardas Berankis.

Matthias Bachinger will be Nishikori's semi-final opponent after he sent fellow German Yannick Maden packing.