Marcel Kittel was unbeatable in Tuesday's sprint finish at the Tour de France, according to the man who took second place.

The burly German cantered to a fourth stage win of the Tour at the end of Tuesday's 178km 10th stage from Perigueux to Bergerac, as Chris Froome retained his overall lead.

Kittel's compatriot John Degenkolb took second, ahead of Dutchman Dylan Groenewegen in third, and then admitted that it wasn't possible to beat his countryman.

"When I was going in the last kilometre, I thought the sprint was already over, but then a miracle happened and Marcel overtook me!" Degenkolb said ironically.

"I did a full sprint to stay on his slipstream and that took me to second place. Today he was unbeatable, that's for sure."

The 29-year-old Kittel was imperious, winning easily as he accelerated from six bodies back to streak several bike lengths clear.

"It's true, it's amazing, I can't even tell you how proud I am," said the Quick-Step sprinter.

"It's a fourth stage win in 10 days, that's a great achievement for me and the team."

It was the manner of Kittel's victory that was most impressive as he even had time to raise his arms in celebration before crossing the line.

- 'I'm the strongest' -

It means he is well set to make this his best Tour yet as he has already matched his previous top effort -- four stage wins in both 2013 and 2014 -- less than half the way through this year's race.

"I think I can say I'm the strongest Marcel at the moment, I've never felt better," he said.

"I'm in a very good condition, that's something for me that's also a big achievement. That gives me also confidence."

Kittel has won four of the five flat sprint finishes at the Tour this year, and in the only one he didn't claim, he was held up by a crash in the final kilometre

A tilt at the record of eight stage wins from a single Tour has now become a viable possibility, but he isn't thinking about such issues.

"For me it's not about being legendary, a VIP or a person of history. I'm just concentrating on what I like doing best, which is sprinting."

Kittel also broke the record for stage wins by a German, moving one clear of the 12 mark he had shared with Erik Zabel following his stage victory on Friday.

And he stretched his lead in the green jersey competition to more than 100 points over Australian Michael Matthews, increasing the possibility of Kittel holding it all the way to Paris -- although he has a fair way to go to match Zabel's record of six wins in that category.

"Even on stage 20 something can go wrong, or stage 21," he warned.

"I prefer to act like I don't have the green jersey on my shoulders because, as we saw the other day with the GC guys, the race can be quickly over."

Earlier in the day French pair Yoann Ofredo and Elie Gesbert took off from the get-go and held a lead of five and a half minutes at one point, but their effort was always doomed to failure and they were inevitably caught with seven kilometres left.

For Briton Froome, the reigning champion, and the other overall contenders it was a quiet day in the saddle.

Following Monday's rest day, Froome admitted Tuesday's stage "almost" felt like a second successive day off.

"It was a calmer day, there wasn't much wind and no stress today -- it was a less complicated stage.

"It's never easy but today was calmer."

That would have been a relief after Sunday's calamitous stage that saw five riders crash out, including Australian contender Richie Porte.

Froome kept hold of the race leader's yellow jersey with an 18-second advantage to Italy's Fabio Aru.

France's Romain Bardet is third at 51sec.

Source: AFP