Italy's Fabio Aru accelerated away from three-time Tour de France champion Chris Froome and other top contenders for the yellow jersey in an impressive show of strength on the first mountain climb of this year's race, winning Stage 5 on Wednesday and showing that he could be the man to beat to the finish in Paris on July 23.

Froome still rode well enough up the steep ascent to the Planche des Belles Filles ski station to take the overall race lead and its yellow jersey off the shoulders of his teammate Geraint Thomas, who couldn't stay with the leaders on the climb made doubly punishing by the hot temperatures.

But it was Aru who impressed with his fierce burst of speed that left everyone in his wake with more than 2 kilometers (1 1/2 miles) left to climb, rising out of his saddle and rocking powerfully from side to side as he ate up the mountain, in his jersey in Italy's colors of green, white and red.

"It's extraordinary for me to win this stage," said the 26-year-old rider for the Astana team.

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Dan Martin of the Quickstep team was second to the top, surprising Froome with his own burst of speed on a very steep section toward the top. Froome came in third - made painfully aware by the climb that the Tour could be harder than ever to win this year.

"This is going to be the hardest-fought battle I've had," he said.

When Aru powered away, lucid enough despite the fierce effort to yell at a roadside spectator who got too close to him and toss a waterbottle at the feet of another, Froome and other top contenders didn't react.

"When he left I stayed with my team and waited for the attack from the others," Froome said. "But no one moved. I thought, 'OK, I have to go, what can I do?'"

Although Froome upped his tempo, leaving his teammate Thomas behind, it was already too late: Aru was gone.

"There's a flat before the last climb and perhaps we waited too long there," Froome said.

But getting the yellow jersey was some consolation. Froome has a 12 second lead over Thomas, with Aru climbing to third in the overall standings, 14 seconds behind the reigning champion for Team Sky.