Bagnères-de-Luchon, France (AFP) – Frenchman Julian Alaphilippe, of the Quick Step team, soloed to victory on a drama-filled Tour de France 16th stage Tuesday after capitalising on a late crash by Britain's Adam Yates (Mitchelton).

Climbing specialist Alaphilippe, claiming his second stage win of the 105th edition, finished nearly 20 seconds ahead of a small group of chasers on the first of four days in the Pyrenees.

"I'm delighted," said Alaphilippe. "It was really hard to get into the early breakaway and for the rest of the day, I was suffering."

Yellow jersey holder Geraint Thomas (Sky) crossed the finish line nearly nine minutes in arrears after yet another stage in which his race lead did not come under threat.

But the Welshman was one of several riders left requiring treatment after tear gas got in his eyes and throat when national gendarmes sprayed tear gas in a bid to clear protesting farmers from the road, which they had blocked with bales of hay around 26km into the 218km ride.

"I felt a tingle in the eyes, and in the back of my throat. I used some water to wash it out," said Thomas.

"But I was alright in the end."

Ahead of stage 17 on Wednesday, described as the most decisive stage in the final week, Thomas maintained his 1min 39sec lead on four-time champion and teammate Chris Froome.

Dutchman Tom Dumoulin (Sunweb) is still third at 1:50.

But on a day that saw Slovakian Peter Sagan mathematically secure his sixth green jersey for the points competition, the day belonged to Alaphilippe.

The 26-year-old Frenchman has spent the past days chasing points to add to his collection for the King of the Mountains' polka dot jersey.

But determination, and good luck combined to hand him his second victory days after his stunning solo ride into Le Grand Bornand on stage 10.

Gilbert Plunges Into Ravine

Yates was on his own and in the lead when he crashed on the descent of the Col du Portillon, the fifth and last climb of the day, his front wheel skidding away from under him as he negotiated a left-hand bend.

Just as Yates got back on his bike, Alaphilippe sped past, looked around at the Englishman and surged ahead.

"I was going to wait for him because it's never great to crash," added Alaphilippe, considered a faster finisher than Yates.

"But I looked back and saw he was suffering, and looked a little scared so I continued."

Alaphilippe had plenty of time to soak up his second win of the race.

"It's fantastic. I'm really happy," added Alaphilippe, who also had some kind words for teammate Philippe Gilbert.

The Belgian was solo and in the lead with 57km remaining when he skidded and flew over a parapet and into a ravine.

He required help to climb back out but, once back on his bike, the former world champion bravely finished the stage.

"I hope he's okay after what happened," said Alaphilippe.

Stage 17 features the only remaining summit finish on the race and, at 65km long, Thomas is expecting fireworks from the word go.

"It will be a tough day, a good two hours of climbing," said Thomas.

"There's no point in going too hard too soon because the last climb is very hard.