Ireland's Dan Martin has finished second on the eighth stage of the Tour de France, 13 seconds behind Team Sky's Chris Froome.

The two-time winner and defending champion led a select group of riders over the top of the Col de Peyresourde and immediately accelerated away, ultimately taking victory from Etixx QuickStep's Martin, who led the chasing pack home.

With BMC's Greg Van Avermaet dropped early on a challenging day in the Pyrenees, Froome assumes the overall lead of the race.

Martin moves up to fourth place overall, 17 seconds down on Froome.

Adam Yates and Joaquim Rodriguez, of Orica-BikeExchange and Team Katusha respectively, are both one second ahead of Martin in second and third position.

In Froome's previous Tour wins in 2013 and 2015, he took control of the general classification battle by winning the first summit finish of the race, but here he made his move a day early as he chose the long descent off the last of the day's four categorised climbs.

As Movistar's Nairo Quintana reached to grab a water bottle at the summit, Froome burst clear and he showed his was willing to take risks on the 16km descent to the line.

Hunched over his bike but still pedalling, the 31-year-old barrelled down the mountain at speeds topping 80kmh as he edged further and further clear of the chasing pack, with his lead reaching 22 seconds before falling slightly on the flat.

"It wasn't really planned," Froome said. "I thought I'd give it a try in the downhill as the few tries on the climb didn't work out. They were sticking to us. So I decided to give it a go in the descent. It was cool.

"Bike racing is just fun, but maybe I spent a little bit too much. Tomorrow is a hard stage but I take every second I can. It's just a really good feeling to win. The guys rode all day so I did it for them."

Martin led home the chasing pack which included GC hopefuls Quintana, Tejay Van Garderen (BMC), Fabio Aru (Astana) and Romain Bardet (AG2R La Mondiale).

Yates was also there to strengthen his hold on the white jersey he took on Friday in spite of his bizarre crash with the flamme rouge banner as it collapsed near the finish line in Lac de Payolle.

Ireland's Sam Bennett finished the stage in the final group in 161st place, 39'24 down on Froome. He is in 197th place overall.