A French police officer is being questioned after a 19-year-old man was allegedly shot dead as he attempted to flee a traffic stop for speeding, prosecutors said.

The victim was among three people in the car when police tried to stop them near Cherbourg-en-Cotentin in Normandy, western France late on Sunday, the state prosecutor Pierre-Yves Marot said in a statement.

The driver allegedly refused to stop and continued driving, before then being halted by a second police car, according to the statement. All three occupants of the vehicle then attempted to flee on foot, it added.

One escaped, another was detained and another was allegedly shot by an officer in the chest, the prosecutor’s office said. The victim has not been named.

"The third person, a 19-year-old from Cherbourg-en-Cotentin, was confronted by officers from the second patrol and knocked into one them while trying to flee," the prosecutor alleged in quotes cited by the AFP news agency.

"The officer then used a stun gun" while a colleague drew and "used her service weapon, fatally striking him in the chest", it added.

The officer was being held for questioning on Monday evening by the internal affairs department of police regulator IGPN.

It comes almost a year after intense and widespread rioting swept across France following the shooting of a 17-year-old during a traffic stop in the Paris suburb of Nanterre. A policeman was charged with homicide.