The group of 12 children, aged 8 to 11, was heading from a leisure centre to a park mid-morning when a woman driving a yellow hatchback hit them at a roundabout in the west coast city of La Rochelle, officials said.

Seven children were hospitalised after the front-impact accident with the car.

A jumble of cycling helmets, a fluorescent yellow vest and tangled bicycles could be seen at the scene, according to an AFP correspondent.

Around 40 firefighters and several ambulances were dispatched to the site of the accident.

One girl was airlifted to hospital in the city of Tours, local official Emmanuel Cayron told reporters. Two others were labelled an “extreme emergency” and also rushed to hospital.

Four other children were hospitalised in La Rochelle, Cayron said.

“The toll is very heavy,” he said. “Our priority was to rescue the children, and also to take care of those who were not physically injured but very shocked by this accident. The scene was harrowing for all those who have seen it.”

The children were hit on a two-way traffic lane, according to prosecutors, who opened an investigation into unintentional injuries. The immediate reason for the collision was not known.

The mayor’s office said the children, who regularly travelled on bicycles, were accompanied by two activity leaders. They wore helmets and reflective vests.

The section of the avenue where the accident took place does not have a cycle lane, according to the town hall.

“It’s planned but not at this time,” said Catherine Leonidas, a deputy mayor.

A resident who gave only his first name, Yann, said the woman drove in the opposite direction. “She no longer knew what she was doing,” he told AFP.

“I heard the sound of the impact, I heard the screams,” he said. “It’s not the first time this has happened. There have been four accidents in five years on this avenue because people drive too fast.”

The motorist was initially placed in police custody but was later hospitalised and could not be questioned.

“The driver, aged 83, tested negative for alcohol and narcotics,” regional prosecutor Arnaud Laraize said in a statement.