French authorities arrested more than 450 people on Thursday in the most violent day of demonstrations since the start of the year against the bill to raise the retirement age from 62 to 64.
In the days leading up to Thursday's protests, rights watchdogs had expressed worries over what they termed "arbitrary" detentions and the police's excessive use of force.
But security officials have defended their actions, saying they are responding to violent rioters and anarchist groups which frequently infiltrate French demonstrations to provoke clashes.
The French Human Rights League has accused the authorities of "undermining the right of citizens to protest by making disproportionate and dangerous use of public force".
"The authoritarian shift of the French state, the brutalisation of social relations through its police, violence of all kinds and impunity are a major scandal," the league's president Patrick Baudouin said on Friday.
Rights groups have raised concerns over the police's repeated use of "kettling", also called "trap and detain" in the United States, a crowd-control tactic consisting of cordoning off protesters in a small area.
Reports have emerged that police have detained foreign schoolchildren and other innocent bystanders, fired teargas at protesters in closed-off areas, and even hurt a man so badly he had to have a testicle amputated.
- Teenagers, jogger detained -
Macron's government on Thursday last week used a controversial executive power to adopt the pensions bill without a parliamentary vote, fuelling outrage and spontaneous protests in major cities.
In the days since, videos have appeared on social media appearing to show police knocking over or hitting demonstrators.
Human Rights Watch told AFP it was very concerned about "what appears to be abusive police practices".
It said they echoed similar "abusive crowd control and anti-riot tactics" during the anti-government "Yellow Vest" movement in 2018-2019 during Macron's previous term in office.
"The French authorities have apparently not drawn lessons from this or reviewed their police crowd control policies and practices," HRW's France director Benedicte Jeannerod said.
Critics have denounced police carrying out sweeping "preventive" detentions, saying even blameless passersby have been caught up in their dragnet.
In one instance on Thursday night last week, two 15-year-old Austrians on a school trip were among those kettled by police, Liberation newspaper reported.
The two teenagers, who had been trying to find their host families, spent the night in jail before their embassy intervened.
A man out jogging was detained the same night.
He told France Inter radio he was booked on allegations ticked at random on the charge sheet, and was not released until the following afternoon.
Security forces detained 292 people that night, but 283 of them were freed without charge.
- 'View to commit violence' -
Macron on Friday condemned the violence overnight and said security forces had worked "in an exemplary manner".
Interior Minister Gerald Darmanin said the police had responded to "troublemakers, often from the far left", who had caused 441 police to be injured.
AFP saw suspected anarchists and other protesters setting fire to rubbish, smashing shop windows and launching stones and fireworks at security forces.
Darmanin said that 11 internal inquiries had been opened into alleged police brutality in the past week.
"It is possible that, individually, police, often because they are tired, commit acts inconsistent with what they were taught," he said.
In one such case, a woman had complained that a member of a motorbike unit beat her with a truncheon while she was caught against a wall in Paris on Monday, a source following the file told AFP.
In another, earlier this year, police on January 19 beat a man so hard with a truncheon that he had to have a testicle amputated, his lawyer told AFP.
Paris police chief Laurent Nunez said earlier this week said there were "no unjustified arrests", and that security forces detained people from "gatherings with a view to commit violence".
He defended the police's motorbike unit, known as BRAV-M, which critics have called to be disbanded, as being one "particularly well adapted to dispersing" groups.
Right groups have long accused French police of brutality and racism in the force, but say internal investigations seem to result in few sanctions.