Mercedes driver Lewis Hamilton has claimed an unlikely pole position for the German Grand Prix this afternoon after a double mechanical blow for Ferrari.

The Italian team had been fastest throughout practice at Hockenheim, but mechanical issues affected both of their cars.

Sebstian Vettel will start his home Grand Prix at the back of the grid after suffering a turbo problem, while team mate Charles Leclerc added to the team's woes when he was sidelined in the final shootout for pole position, stepping out of his car without setting a timed lap.

Ferrari said Vettel, a four-times Formula One world champion, had suffered a problem with the air flow to the car's turbo.

The German, who started last year's race on pole position but crashed out while leading, has not won since the Belgian Grand Prix last August.

Vettel reported a loss of power on the radio shortly after he left the pits for his first run during the opening phase of qualifying.

"I don't know what happened," Vettel told Sky Sports television.

"Something broke with the turbo and it was game over from there. Obviously I'm very bitter, I think the car is great and we've lost out on a big chance but hopefully we'll have a big one coming again tomorrow.

"I'm looking forward to the race, but obviously it would have been nicer to start at the very front than the very back but we'll see what happens."