WALES' reigning Tour de France champion Geraint Thomas has been taken to hospital for assessment following a crash which has forced him to pull out of the Tour de Suisse.

The Welshman, from Cardiff, came off his bike around 30 kilometres from the end of stage four of the race and received medical attention at the side of the road.

Team Ineos reported the 33-year-old remained conscious following the incident.

"Sadly @GeraintThomas86 has been forced to abandon the #TourDeSuisse. He was alert and speaking to the team after the crash and will be taken to hospital for checks. Further updates to follow," read a tweet from Team Ineos.

According to cyclingnews.com, Tour de France champion Thomas suffered cuts to his back and above his right eye.

He is due to lead Ineos at this year's Tour, which takes place next month, after team-mate Chris Froome last week crashed while in France for the Criterium du Dauphine.

Froome underwent extensive surgery following his high-speed crash, which left him with multiple injuries, including a broken femur.

Deceuninck-Quick-Step rider Elia Viviani went on to claim the stage win in Switzerland following a sprint finish in Arlesheim ahead of Michael Matthews (Sunweb) and overall race leader Peter Sagan of Bora-Hansgrohe.

Viviani was set up by good work from team-mate Michael Morkov during the closing 1.5kilometres, the Italian staying close to the barriers on the left, while Matthews was able to outpace Sagan in the dash for the line.

Sagan retains the overall lead, ahead of Australian Matthews by 10 seconds, with Kasper Asgreen (Deceuninck-Quick-Step) in third.