Spain's Carlos Barredo and Portugal's Rui Alberto Costa were involved in a punch-up at the end of the Tour de France sixth stage on Friday and were fined by organisers.

Barredo, who races for Quick Step, and Caisse d'Epargne rider Costa came to blows after the finish line over a race incident.

Barredo ran towards Costa brandishing his front wheel and attacked him. After a flurry of punches were exchanged the two were separated by officials.

"Son of a ...," Barredo shouted at Costa.

They were both handed fines of 400 Swiss Francs ($381) for 'insults, threats and incorrect behaviour'.

"I was told by a race steward that one of my riders had been involved in a fight but I don't know the circumstances," Caisse d'Epargne team director Yvon Ledanois told Reuters.

"I suppose they were involved in a race incident and that with the sun, spirits heated up. I want to talk it over calmly with Rui in the hotel," he added.