PARIS (Reuters) - Workmen erected metal barriers and plywood boards on the glass-fronted facades of restaurants and boutiques lining the Champs Elysees on Friday ahead of a second demonstration in the French capital by protesters angry at high fuel prices.

For more than two weeks, the “yellow vests” have blocked roads across France in a spontaneous, popular rebellion against diesel tax hikes and the high cost of living. It has grown into one of the largest and most stubborn challenges Emmanuel Macron has faced in his 18-month-old presidency.

A week ago thousands of protesters, who have no leader and have largely organized themselves online, converged on Paris for the first time, turning the Champs Elysees into a battlezone as they clashed with police firing tear gas and water canon.

For now, the “yellow vests” -- who take their name from the high-visibility jackets all motorists in France must carry in their vehicles -- enjoy widespread public support.

“I completely agree with the protesters,” said one shopper on the Champs Elysees who identified herself only as Brigitte. “It’s regrettable to see measures being taken against possible damage, but I support the movement.”

When they began, the protests caught Macron off-guard just as he was trying to counter a plunge in popularity, with his approval at barely 20 percent. His unyielding response has exposed him to charges of being out of touch with common folk.

The outburst of anti-establishment anger is strongest in rural villages, provincial towns and sprawling city outskirts, and mirrors the disconnect between urban elites and alienated voters that has spurred the rise of populist forces across Europe, in the United States and in Britain’s Brexit vote.

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NO BACKING DOWN

Meeting French expatriates in Buenos Aires ahead of a G20 summit, Macron said he understood the “legitimate anger, impatience and suffering of people who wanted to live better” but said there would be no about-turn in policy direction.

“It will fall on me to take additional steps in the weeks and months to come, but they will never be a step backwards,” said the 40-year-old former investment banker.

The “yellow vests” have also inspired protests next door in Belgium, where on Friday demonstrators hurled rocks at the prime minister’s office.

France’s Interior Minister Christophe Castaner said the Champs Elysees would be closed to traffic, and pedestrians would be funneled through checkpoints. Several thousand police officers will be deployed along the two-kilometer avenue.