Two riders have been expelled from the Tour de France after a fiery exchange late in Stage 17.

Welshman Luke Rowe and German Tony Martin were kicked off the race after clashing on the last climb of a hot 200km journey from Pont du Gard to Gap.

The tension escalated when Martin, riding for Jumbo-Visma, ran an advancing Rowe off the road by swerving to his right as the pair fought to gain front position.

Team Ineos' Rowe, who was attempting to move his teammates to the head of the race, had to correct himself to avoid crashing off the bitumen.

Cameras then caught Rowe raising his hand to Martin's face moments later before the pair were caught shoulder to shoulder at the front of the peloton as they clashed for the third time.

After completing an anti-doping test at the finish, Rowe walked into the UCI's video review truck where he watched footage of the incidents with Team Ineos boss Dave Brailsford and sports director Nicolas Portal.

Rowe initially tried to play down the incident.

"It was nothing really. I rolled over the line with him, it's all good, we shook hands," Rowe said after the stage.

"We're both doing the same role. We just got in each other's way. That's bike racing. It's all good."

But the UCI disagreed, later releasing a statement confirming both riders had been expelled from the race.

They had also been fined $1500 (AUS) each and docked ranking points under Article 8.2.1, which covers assault, intimidation, insults, threats and behaviour that is indecent or that endangers others.

Team Ineos was last night understood to be considering an appeal, 12 months after they lost Gianni Moscon when he was expelled for attempting to hit another rider.

Race leader Julian Alaphilippe could be seen talking to Tony Martin shortly after the incident and later said he wasn't impressed.

"There was a lot of tension in the peloton at that stage - everyone wanted to be well positioned - and I saw something I don't like to see," Alaphilippe said.

"There were riders who were too nervous, touching each other. Maybe they were scared I was going to attack, so I just tried to calm them down. I told them not to take any risks, because the riders in the break were no threat and I wasn't going to attack. I just called for calm."

Martin did not speak after the stage, but Jumbo-Visma's leader Steven Kruijswijk said Ineos "didn't like it" that his team were riding on the front.

"The two of them didn't want to concede any ground to each other, and then it's two guys who don't want to give the other space," Kruijswijk said.

"That happens - perhaps it was the heat, or a bit of irritation."