The French government on Wednesday attempted to head off planned protests over rising fuel costs by announcing a series of measures to help poorer families pay their bills.
A surge in the price of diesel has provoked an uproar in rural and small-town France, with citizens' groups threatening to block roads and highways on Saturday over what they call President Emmanuel Macron's anti-car policies.
The "yellow vest" movement, named after the high-visibility jackets worn by protesters, is the latest to rattle Macron's centrist government.
Around 600 protests are planned around the country on Saturday.
Prime Minister Edouard Philippe on Wednesday ruled out a U-turn on higher taxes on diesel, considered a major source of air pollution, but promised to do more to help poor families shoulder the cost.
"We have heard the need of the French to be assisted in the (ecological) transition, which is difficult," he said.
With the rising cost of living emerging as one of the biggest challenges of Macron's presidency, Philippe announced that 5.6 million households would receive energy subsidies, up from 3.6 million currently.
The state will also double the scrappage bonus on polluting vehicles for France's poorest families, expand the scheme to target one million motorists in total over five years and introduce fuel tax credits for those who use their cars a lot for work.
- 'Fed up' -
The measures appeared unlikely however to appease the "angry vests", who have tapped into frustration with Macron's policies, seen as favouring high-earners in cities over the rural population and the poor.
The leader of the protests in the central-eastern Dole region, Fabrice Schlegel, said he hoped some 1,500 cars would turn out to snarl traffic on Saturday.
"We've been scorned for years; for years we've been talked down to. It's time for us, the little people, the non-political, non trade-union people, to rise up," he told a recent rally.
In 2013, a protest by the Breton 'Red Caps' over an environmental tax on trucks led to running battles between police and demonstrators.
The Socialist government of then President Francois Hollande eventually backed down.
During a tour of the provinces last week to try reconnect with rural voters, Macron -- whose approval ratings have sunk to under 30 percent -- was repeatedly harangued over fuel prices.
The price of diesel has risen around 23 percent over the past 12 months to an average of 1.51 euros ($1,70) per litre -- its highest point since the early 2000s.
But France's reform-minded president is also taking heat from environmentalists, who accuse him of not living up to his promise to "Make Our Planet Great Again".
Opposition parties from both the left and the right have sought to tap into the discontent.
Laurent Wauquiez, leader of the main opposition Republicans party, on Wednesday called on the government to cancel another planned increase in the carbon tax on fossil fuels to offset rising petrol prices.
"This government is going to take 15 billion euros from French pockets and the prime minister this morning talks of handing 500 million back, that's not even three percent," Wauquiez, a conservative, said on BFMTV.
Eric Coquerel, a law-maker from the radical left France Unbowed, said the French were "not just mobilising because of petrol prices.
"They are fed up," he declared.