A fan trying to take a selfie caused a crash on stage 15 of the Tour de France with about 20 riders involved in the incident and coming off their bikes.

With about 125km remaining Team Jumbo-Visma rider Sepp Kuss had his handlebars knocked by a supporter who was holding out a phone.

Kuss swerved into team-mate Nathan van Hooydonck who fell off his bike, causing a crash behind him.

All the riders who fell in Sunday's crash on the 179km stage from Les Gets les Portes du Soleil to Saint-Gervais Mont-Blanc were able to continue, including 2019 champion Egan Bernal.

General classification leader Jonas Vingegaard and second-placed Tadej Pogacar were unaffected.

The official Tour de France Twitter account posted a slow-motion video of a rider ducking under a spectator's outstretched arm with the message: "Please pay attention to the riders."