Four people have been stabbed near the former offices of the Charlie Hebdo satirical magazine in Paris.
The publication was attacked by Islamist militants five years ago.
Cops in the French capital say a suspect has been arrested over today's incident.
A police source said that two of the four wounded had life-threatening injuries.
One witness told Europe 1 radio: "I was in my office.
"I heard screams in the road. I looked out of the window and saw a woman who was lying on the floor and had taken a whack in the face from what was possibly a machete."
"I saw a second neighbour on the floor and I went to help."
Paris police said one person had been arrested near the Bastille opera house.
A police source said a machete had been found at the scene.
Another police sources said a meat cleaver had been found there.
Local authorities asked people to avoid the area and said a police operation was under way in a northeastern district of Paris.
Deputy mayor Emmanuel Gregoire tweeted that police were hunting a "potentially dangerous" individual.
The Paris metro closed lines in the area.
Fourteen people went on trial in Paris on September 2, accused of being accomplices in the attack on the Charlie Hebdo offices in January 2015 that killed 12 people.
The court heard that they had sought to avenge the Prophet Mohammad, nearly a decade after the weekly published cartoons mocking him.
