Switzerland cyclist Simon Pellaud has failed to finish the road race after suffering with a sore stomach during the race.

Pellaud was in the leading pack with just 40km left in the race, but was forced to withdraw.

"I am really pissed because I had done the perfect race. I was in the breakaway with some really strong guys in the front. And then I had some really bad pain in my belly and I had to shit in my pants on the cobbles. It was really, really bad," Pellaud told reporters.

"I asked the doctor to get the pill but it was too late. I could not really eat. I felt so bad. Now I have taken a shit so I feel better.

"I just wanted to put my nose in the wind and ride as fast as possible until the end. I think it was a big opportunity for me and I've missed it. I've never been so sad like this after a race."

The 22-year-old won the 2013 Swiss Under-23 championships.