Froome crossed the line ahead of BMC's Richie Porte, but with Thomas down in 10th place the Welshman surrendered the race lead he took in Saturday's opening time trial in Dusseldorf.

Three-time Tour winner Froome now leads by 12 seconds from Thomas, with Aru up to third, 14 seconds back, after the Italian national champion won his first career Tour de France stage.

The strength of Aru's attack will certainly have caught the attention of his fellow contenders as the 27-year-old burst clear with 2.4km left and won by 16 seconds from Martin, with Froome leading Porte over the line another four seconds back.

Martin said: "It was a cat and mouse game when Fabio went. We kind of looked at each other. He was super strong so congratulations to him. I knew I just had to wait for a sprint and if Fabio was close enough I'll be able to catch him but in the end it didn't work out."

Romain Bardet, France's great hope for a home win, was fifth on the day, just ahead of Britain's Simon Yates and former Team Sky man Rigoberto Uran and two-time Tour winner Alberto Contador.

But Nairo Quintana could only manage ninth place, 34 seconds behind Aru, as his hopes of contending suffered another blow.

Martin is up to fourth place overall, 25 seconds back. The Quick-Step Floors man is 14 seconds ahead of Porte and 18 ahead of Orica-Scott's Simon Yates, who moves up to sixth overall and takes over in the white jersey as the best young rider - a category won by his twin brother Adam 12 months ago.