French President Emmanuel Macron on Wednesday sounded the alarm on the "unprecedented" situation caused by fuel price protests in recent weeks, denouncing what he described as "great violence."

Midway between riots in Paris on Saturday and further protests expected next weekend, Macron warned ministers that some of those involved had "one sole objective: to attack the republic," government spokesman Benjamin Griveaux said after a weekly cabinet meeting.

The president told ministers that it was not a time not for "political opposition but for [supporting] the republic," Griveaux said.

Prime Minister Edouard Philippe on Tuesday announced a six-month moratorium on the petrol and diesel tax rises that initially sparked the "Yellow Vests" protest movement.

It was a rare backdown by Macron, who dislikes acting under pressure, and came days after rioters fought running battles with Paris police that saw more than 100 people injured and over 400 arrested.

But multiple individuals who claim to represent the leaderless movement, which is organized largely by social media and word of mouth, have called for further protests on Saturday all the same.

Macron has not spoken directly to the public since returning from the G20 summit in Argentina after Saturday's riots, although on Tuesday he visited a government building that was partly burned during unrest in a provincial town.

The president "asked the political forces, the trade unions, and business leaders to launch a clear and explicit call for calm and for respect of the republican order," Griveaux said.

Earlier, the head of France's main opposition party called for a state of emergency to be declared ahead of Saturday's expected protests.

"That would enable the security forces to be protected and it would also enable us to protect those who want to march peacefully without being taken hostage," Laurent Wauquiez of the conservative Les Republicains party told France 2 television.

"What I do not want is for our country to plunge into chaos," Wauquiez added.

Wauquiez called on Macron to address the situation after almost three weeks of protests around the country and said Philippe's announcement of a moratorium was not enough.

"The French don't want this tax. Putting it back six months doesn't make sense, it must be cancelled," Wauquiez argued.