French police are holding a man on suspicion of firing a shotgun at the offices of a left-wing newspaper and a major bank in Paris, judicial sources said.
The suspect was arrested this evening in his car in a car park lot of a Paris suburb, one source said.
A second source said the man was thought to be under medication and was not in a state to be questioned immediately.
Police are testing his DNA against traces found on cartridges left behind by the gunman.
The gunman seriously wounded a 23-year-old photographer's assistant in the lobby of the Liberation newspaper on Monday before fleeing.
Shortly afterwards, he fired at least three shots into the lobby of the headquarters of Societe Generale in the La Defense business district. There were no casualties.
The gunman later vanished into the crowds of Paris' Champs-Elysees boulevard after forcing a driver at gunpoint to take him there.
Police detained a suspect at an underground parking lot in the western Paris suburb of Bois-Colombes.
The man bore a "strong physical resemblance" to the gunman suspected of carrying out several recent attacks in the French capital, the Paris prosecutors' office said.
Prosecutors said the man was not immediately in a position to be questioned and that the reading of his rights had been deferred, but provided no explanation
With a vast manhunt under way, police have received hundreds of tip-offs from the public after circulating photographs from security cameras, including some of his face.