In London, a woman wearing a Charlie Hebdo T-shirt was attacked with a knife.
The 39-year-old was treated in hospital with minor head injuries after the attack, the police said on Monday.
The perpetrator was able to escape, the knife was seized at the crime scene.
The act took place on Sunday afternoon in the "Speakers' Corner" of London's Hyde Park, where speeches and debates are traditionally held in the open air.
A video of the incident uploaded to YouTube shows a black-clad man with a hood approaching the woman and apparently stabbing her several times before fleeing.
The woman wore a T-shirt with the logo of the French satirical newspaper Charlie Hebdo and the slogan “L'amour plus fort que la haine” (“Love is stronger than hate”).
In 2015, twelve people were murdered in an Islamist attack on the Charlie Hebdo editorial team.
The satirical newspaper had become a target because of the publication of Mohammed cartoons, among other things.
The police did not provide any information about the woman's identity, but online networks said it was Hatun Tash, a Christian activist from a group called "DCCI Ministries".