Thomas extends Tour lead

Geraint Thomas became the first man to win up l'Alpe d'Huez with the yellow jersey on his shoulders on Thursday as he extended his Tour de France overall lead amid unsavoury scenes while sparking fresh questions about the Team Sky leadership.

Thomas, who took the yellow jersey when he won Wednesday's 11th stage, prevailed again in the 12th at top of the 21-hair-pinned climb, one of the most iconic of the Tour.

But the Welshman was heavily booed by the crowd at the podium ceremony while his Team Sky leader, fellow Briton and reigning champion Chris Froome, who finished fourth, was also jeered all the way up the famous ascent.

Thomas accelerated in the last stretch to beat Dutchman Tom Dumoulin and France's Romain Bardet who were second and third, two and three seconds behind respectively. Froome was also three seconds off the pace as the boos came from the crowd.

The four-time champion was constantly jeered on the last stretch, a 13.8-km effort on an average gradient of 7.9 percent, with one spectator hitting him on the shoulder.

"Obviously it's not nice (the boos) but everyone is entitled to their opinion, but we need to be safe," said Thomas afterwards.

Overall, Thomas leads Froome by one minute 39 seconds and Dumoulin by 1:50.

Former champion Vincenzo Nibali crashed with about four kilometres left and ended seventh, 13 seconds off the pace.

"There were two police motorbikes and the road became narrow, there were no barriers and Froome attacked, traffic slowed down and I fell. My back hurts. I had trouble breathing and now I don't feel well standing," said the Italian.

Thomas, who did not respond to Froome's attack, said on Wednesday the four-time champion remained the team leader, but he appeared to be the strongest rider at l'Alpe d'Huez.

"In my eyes, Froomey is still our leader," said Thomas.