Tour de France 2015: Chris Froome extends lead over 2014 champion Vincenzo Nibali

Chris Froome retained the Yellow Jersey with another show of strength at the Tour de France.

The 2013 champion showed he is in peak form as he attacked on the steep climax to stage eight at Mur de Bretagne.

And though Froome saw Alexis Vuillermoz power to the first home win on this year's Tour, defending champ Vincenzo Nibali again struggled.

The Italian lost a further 10 seconds to Froome just days after he was well-beaten on the equally-tough finish at Mur du Huy in Belgium.

Froome came home eighth after the 112.7miles stage from Rennes in scorching conditions in Brittany to retain his 11 secs lead over Peter Sagan.

The Slovak missed the chance to claw back four bonus seconds on the Team Sky rider after being pipped for third by Movistar's Alejandro Valverde.

But in the battle for the General Classification, Froome is now one minute 48 secs ahead of Nibali heading into Sunday's team time trial.

Nairobi-born Froome, 30, said: "That was a tough climb, but my team-mates did a great job to bring me to the front.

"I wasn't trying to win the stage, just concentrating on my own battle for the GC. Congratulations to Alexis as it was a magnificent effort.

"I feel really good at the moment, but whether I am better or worse that when I won it, we'll see when we get to the mountains.

"There is a long way to go yet. We have still to get to the Pyrenees.

"That's when the battle for the maillot jaune will commence.".

Nibali, who looked so strong last year when he dominated the Tour after Froome and Alberto Contador quit, lost contact in the final few hundred yards on the steep gradient.

The other main contenders, Spaniard Contador and Nairo Quintana, came home in the same group as Froome to remain 36 seconds and one minute 56 seconds behind respectively.

The biggest disappointment of the day fell to Ireland's Dan Martin who had high hopes of a victory but came home second five seconds down.

The Cannondale-Garmin rider said: "I knew what I had to do but I couldn't get out.

"I was stuck on the right-hand barrier and I couldn't move. I'm really disappointed because they guys rode incredibly well."