The suspect was captured on security video leaving a bag in front of a bakery shortly before an explosion occurred at around 5.30pm local time on Friday, police sources and local mayor Denis Broliquier said.

Most of those hurt were hospitalised for treatment to leg injuries that were described as light.

President Emmanuel Macron characterised the incident as an "attack" when the news broke during a live YouTube interview ahead of Sunday's European elections. "My thoughts are with the injured," he said.

Paris anti-terrorism prosecutors opened an investigation as police said they were treating the blast as an attempted homicide, and Interior Minister Christophe Castaner headed to the scene.

The partially masked suspect appeared in security camera footage wheeling a bicycle to the scene, before leaving a bag outside a branch of Brioche Doree, a popular bakery chain.

Police sources described the suspected attacker as a European or North African male, seen wearing beige Bermuda shorts, an army-green scarf or head wrap and dark glasses.

Soon after he left, the blast rained metal bolts on passers-by in front of the premises on rue Victor Hugo, several blocks from the city's main station, according to police.

Police forces across France have been instructed to increase security in public places and event venues, Castaner said.

Australian Associated Press