By Julien Pretot
LE-PUY-EN-VELAY, France (Reuters) - Chris Froome survived an attempted coup by Romain Bardet's AG2R-La Mondiale team in a treacherous, hectic 15th stage to retain the Tour de France overall leader's yellow jersey on Sunday.
Dutchman Bauke Mollema, the strongest and smartest of the breakaway riders, who had three top 10 finishes on the Tour, won the 189.5-km stage from Laissac-Severac L'Eglise but the action was elsewhere.
Defending champion Froome was first caught at the end of a split caused by French team AG2R-La Mondiale, who continued to press the pedals when the race leader suffered a mechanical problem shortly before the key climb of the day.
The Team Sky leader kept his cool, however, and powered his way back to stay on top of the general classification with an 18-second advantage over Italian Fabio Aru.
"It was a stressful moment. I thought I might not get back to the front,” said Froome, who takes the yellow jersey into Monday's rest day.
"I'm just grateful I survived today. Tomorrow is a rest day so I will regain some energy and hopefully be fresh for the third week."
Bardet, who enjoyed huge crowd support in his home region in the Massif Central, while Froome was booed at one point, stays third 23 seconds off the pace. Colombian Rigoberto Uran is fourth six seconds further back.
A week after Aru had attacked just as Froome suffered a mechanical problem, the Briton again had trouble with his bike and, as the race was on, none of the main contenders waited for him.
AG2R-La Mondiale accelerated suddenly at the front of the peloton with some 45-km left and Froome and some of his team mates were trapped at the wrong end of the split.
A spoke on Froome's rear wheel broke and he was assisted by team mate Michal Kwiatkowski.
Team Sky's Mikel Nieve and Vasil Kiryienka then pulled Froome along in their wake as they trailed Bardet's group, which contained Aru and Rigoberto Uran, by 45 seconds.
The Briton made up the time on the ascent of the Col de Peyra Taillade, an 8.3-km climb at an average gradient of 7.4 percent, with the help of team mate Mikel Landa, who briefly dropped out of the Bardet group to tow his leader back.
“Never a dull moment in this year’s Tour, that’s for sure," said Froome. "Just coming into the main climb of the day I had a bit of a mechanical problem, I had to change the back wheel, and it couldn’t have happened at a worse time really. It was all hands on deck. I think I'll pass out tonight. I'm knackered."
Bardet and Aru, who opted to stay in the wheels of the Frenchman's team mates in the punishing ascent instead of upping the pace to finish Froome off, jumped away on the final climb but were easily reined in.
Ireland's Dan Martin pedalled away on a flat section after the descent to gain 12 seconds on Froome and the other favorites.
Martin is now fifth overall, 1:12 off the pace.
(Editing by Clare Fallon and Ken Ferris)