Alberto Bettiol was alone in the lead and managed to cycle past the protesters.
He was then asked to stay.
The same thing happened to the remaining cyclists.
After the protesters were removed from the road by French police, the race was resumed with the time differences that applied when the race was interrupted.
According to the website Cyclingnews, the group demonstrated to draw attention to climate change.
Magnus Cort, from Denmark, finally took home the stage before the Australian Nick Schultz after a close sprint battle that required a goal photo.