French President Emmanuel Macron is "very shocked" by images showing Paris police beating up a Black music producer, a government source said on Friday.
French prosecutors are investigating the violent arrest of Michel Zecler, who said he was also racially abused by the officers, after CCTV footage of the incident was released. The police watchdog is also investigating.
Four police officers were being held for questioning as part of the investigation, the Paris Prosecutor's office said.
The beating inside the entrance of a building was captured on closed circuit television and mobile phone footage which circulated online.
The alleged attack on Zecler risks inflaming racial tension with allegations of repeated police brutality against Black and ethnic communities at the forefront of many people's minds after the death of Black American George Floyd in Minneapolis in May sparked the "BlackLivesMatter" movement.
The arrest of Zecler came amid fierce debate in France over draft legislation that would limit journalists' ability to document French police officers at work.
Dominique Sopo, President of anti-racism group "SOS Racisme" told Reuters Zecler had been the target of a "racist attack".
"For police officers to act that way they must have a tremendous feeling of impunity. This situation is a symptom of an impunity that has been going on for too long," he added.
Paris police already faced criticism this week after social media photos and videos showed officers hitting protesters as they cleared out an illegal migrants campsite in a central Paris square.
The music producer told reporters he was set upon by police at his studio in Paris's 17th arrondissement on Saturday.