In Paris, a man was reportedly hit in the face by a rubber bullet fired by a controversial riot control weapon, while in the southwestern city of Bordeaux an MP accused police of assaulting him.
About 39,300 people protested nationwide, including 4,000 in Paris, according to the interior ministry — down on the 46,600 turnout announced the previous weekend.
The official figures are regularly disputed by protest organisers, who argue the government is trying to portray the movement as losing support.
But at least one demonstrator in the capital appeared to acknowledge their numbers were falling.
“We are less numerous than usual, but we are there anyway and that's essential,” said pensioner Murielle, adding: “We won't give up because the situation is not going to improve, that's for sure.”
Regarding the possible police shooting of a man with a so-called defence ball launcher, known by the French abbreviation LBDs, Paris police chief Michel Delpuech said “an internal administrative investigation has been opened”.
The weapons fire 40-millimetre rubber projectiles, considered non-lethal, but have been blamed for serious injuries to a number of demonstrators.
Macron last week rejected a call from rights watchdog the Council of Europe to suspend their use.
Elsewhere in the country, in Bordeaux, an MP from the far-left France Unbowed party, Loic Prud'homme, said police had assaulted him with batons on the edges of a march and that he had filed a formal complaint.
The local regional governor insisted police had intervened to stop protesters taking an unauthorised route and had done their job correctly.
In the western city of Nantes, police fired rubber bullets, tear gas and water cannon to disperse demonstrators, some of whom hurled projectiles including petrol bombs and bottles containing acid.
“There has been a lot of damage… bus shelters, a bank branch, a travel agency, a business,” said Claude d'Harcourt, a regional governor for the Nantes area.
There was also trouble in Nice, Strasbourg and Lille, where protesters marched carrying signs and banners, including “Macron accomplice of the worst scum, finance” and “stop capitalist militias”.
Police used teargas elsewhere in the country, including at protests in Bordeaux, Morlaix, Arles and Lyon.
“Those who are still in the street today will never give up, it's the hard core,” said one demonstrator at the Lyon protest, a farmer from the region.
On Friday, Macron had repeated a call for calm after weeks of “unacceptable” outbreaks of violence.
The protests have also seen spates of vandalism with monuments defaced, businesses damaged and cars set alight.
Macron has pledged 10 billion euros in response to anger over the high cost of living, including tax cuts for some pensioners and measures to boost low wages.
He has also spearheaded a “grand national debate” by way of the internet and town hall meetings to gather opinions on how the country could be reformed.
This week's demonstrations had been billed by organisers as a prelude to a “big month” of protests to mark four months of the “yellow vest” movement and the end of the debates championed by Macron.
Many yellow vest activists dismissed the debates as a platform for Macron rather than a forum for real discussion.
The protests, which have no organised leadership and are named after the fluorescent vests that French drivers must keep in vehicles, began on November
17th over increasing fuel taxes — later reversed by the government.
They quickly grew into a broader anti-government rebellion over anger towards Macron.
Eleven people have died in events linked to the protests since they began.
The number of those attending the weekly rallies has dropped since 282,000 turned out on November 17th.