A Tunis court, which is investigating the incident, has made no mention of whether the victim was one of those who took part in Friday's demonstration.
A Tunisian man has died in hospital from injuries inflicted by police, activists say, in what would be the first death from protests against President Kais Saied's assumption of extra powers.
A Tunis court investigating the death said the man, found in a coma on Mohamed V Street in the capital, was taken to the hospital on Friday and died on Wednesday.
A court statement made no mention of whether the man was one of the demonstrators.
The court said the man's body bore no visible signs of violence and would be handed to forensic examiners to determine cause of death. An investigation had been opened, it added.
There was no immediate comment from the interior ministry.
On Friday, police deployed water cannons and batons against protesters who defied a Covid-19 ban on gatherings, as Saied faced growing discontent over his suspension of parliament last July and subsequent rule by decree.
"Ridha Bouziane, who took part in the January 14 protest, died in a hospital in the capital after suffering serious injuries as a result of the excessive violence by police in the demonstration," the Citizens Against the Coup coalition said.
Samir Dilou and Samir Ben Amor, lawyers for arrested protesters, also said Bouziane died due to police violence, though no more specifics were given.
Saied has said he will uphold all freedoms during a transitional period to a new constitution later this year.