At least one person has died after a car crashed into two different bus stops in different parts of the French port city.
The 35-year-old driver of the vehicle has been arrested and the public has been advised to avoid the Old Port area.
The incident is not currently being treated as terrorism.
A source close to the investigation told Reuters that the suspect was known to police for minor crimes and had psychological issues.
France’s counter-terrorism prosecutor said it had not taken up the case at this stage.
“The arrest was made in a surprisingly calm fashion, no gunshots were exchanged,” David Reverdy, of the Alliance police union in Marseille, told BFM TV.
The driver of the vehicle first hit a bus shelter at about 8.15am local time in the 13th district in the northern part of the city.
An hour later the vehicle was driven into a bus shelter several kilometers to the south.
“The distance travelled by the driver suggests a certain determination,” Reverdy said.
“But we can ask ourselves: why these places? If one wanted to cause carnage, other places in Marseille, at another time of day, would have been more logical,” he said.
France has been under a state of emergency since the November 2015 terror attacks in Paris, which killed 130 people.
The incident comes as Spanish police hunt for the 22-year-old driver who plowed a van into a crowd in Barcelona on Thursday.