French police have launched a manhunt after an explosion injured 13 people in Lyon.

Authorities in France have released images of the suspect, who wore a cap and sunglasses that partially hid his face.

Counter-terror prosectuor, Remy Heitz, said an investigation was launched into the "attempted murderer in relation with a terrorist undertaking".

No group has claimed responsibility of the blast, he added.

Regional authorities said 13 people suffered injured after the explosion on a busy pedestrian street, with 11 still in hospital on Saturday morning.

French President Emmanuel Macron called the explosion an “attack” on Friday.

Thirteen people were injured in the blast in Lyon. Credit: AP

Mr Heitz described video surveillance that shows the suspect heading towards Lyon city centre on a bicycle on Friday afternoon.

The man was seen arriving on foot, pushing his bike, in the pedestrian Victor Hugo street. He was seen leaving a paper bag on a concrete block in the middle of the street near a bakery, Mr Heitz said.

The suspect immediately returned to his bike and left by the same path. One minute later, the explosion shattered the glass of a cooler in the bakery.

Investigators at the scene have found screws, metallic balls, a triggering device that can be used remotely and plastic pieces that may come from the explosive device.

Scene of the explosion in Lyon Credit: Sebastien Erome/AP

Police issued an appeal for witnesses and described the suspect as “dangerous”.

Heitz said police will release more photos soon. The man was wearing a cap and sunglasses that partially hid his face.