French police are hunting a suspected suitcase bomber after an explosion in the central city of Lyon on Friday injured at least seven people, officials say.

Key points: The suspect reportedly left a suitcase which later exploded in front of a bakery

The suspect reportedly left a suitcase which later exploded in front of a bakery French authorities labelled the incident an attempted homicide

French authorities labelled the incident an attempted homicide But they would not confirm French media reports the blast was caused by an exploding package.

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

The partially masked suspect was captured on security video leaving a case in front of a bakery shortly before an explosion at 5:30pm (local time), police sources and local mayor Denis Broliquier said.

Mr Broliquier said he arrived minutes after the explosion, and saw "a refrigerated cooler in the Brioche Doree [bakery], whose windows had been shattered".

"It was the windows … that superficially injured the people who were 1, 2 or 3 metres away," he said.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 27 seconds 27 s Paris's anti-terrorism prosecutor labelled the incident as an attempted homicide. (Photo: Reuters/Emmanuel Foudrot)

Live television images showed the bakery's sign intact and police vans and an ambulance on the street, which had been cordoned off from the public.

The central area, the Presqu'ile, lies between the Rhone and Saone rivers that run through France's third-largest city.

The suspect targeted a bakery in central Lyon. ( ABC News )

Resident Jean-Pierre, who lives above the bakery and did not give his last name, told television station BFMTV the noise from the explosion was "deafening" but it did not cause the walls to shake.

He said one window shattered and there was some debris on the street.

The president of greater Lyon, David Kimelfeld, called for calm.

"We must remain prudent and wait for the analysis of the circumstances and not panic the Lyon population," he said on BFMTV.

President Emmanuel Macron, who was beginning a broadcast address as news of the explosion broke, described the incident as an "attack" with no fatalities.

"My thoughts are with the injured," he said.

The Paris anti-terrorism prosecutor opened an investigation, with police treating the blast as an attempted homicide, law enforcement officials said.

Authorities would not confirm French media reports that the blast was caused by an exploding package.

Members of France's anti-terror squad also attended the scene. ( AP: Sebastien Erome )

AP/Reuters