Geraint Thomas sprinted away from Sky teammate Chris Froome to win the legendary climb on Alpe d'Huez while wearing the yellow jersey in the Tour de France on Thursday.

With questions over which rider Sky is backing for victory, it was a bold demonstration of strength by Thomas, who has been Froome's loyal lieutenant for years.

Tom Dumoulin crossed second, two seconds behind, and Romain Bardet was third, three seconds back.

Froome finished fourth, four seconds behind Thomas, as the 12th stage concluded with the famed 21 bends to the Huez ski resort.

Thomas extended his lead over Froome in the overall standings to 1 minute, 39 seconds.

Dumoulin was third overall, 1:50 behind.

Vincenzo Nibali recovered from a crash in the final kilometers to finish seventh in the stage. The Italian was fourth overall, 2:37 back.

The last and most feared of the three stages in the Alps this year, the 175.5-kilometer (109-mile) leg began in Bourg-Sant-Maurice and took the peloton over three grueling, beyond-category climbs.