By Hajer M'tiri

PARIS

Riots over the fatal police shooting of a young man in western Nantes city continued for a third night, with cars set on fire and clashes between police and protesters intensifying until early Friday morning.

Nearly 50 cars were set on fire overnight and there were arson attempts on a high school and a petrol station, French daily Ouest-France reported.

The 22-year-old slain youth, identified by local media as Aboubakar F. , was killed on Tuesday during a police check of a vehicle after he "refused to comply" with police requests, according to Nantes Prosecutor Pierre Sennes.

The policeman who fired the shot has been detained for questioning by a police oversight body, the IGPN, which is investigating the killing.

Sennes said the officer was being held on suspicion of "voluntary violence by a person in authority leading to unintentional death".

On Thursday evening, around 1,000 people marched in Nantes calling for "justice for Abou" and demanding the circumstances of his death be revealed.

Prime Minister Edouard Philippe, on a visit to Nantes, condemned the riots and promised "the fullest transparency" about the man's death.

Interior Minister Gerard Collomb said the government would do everything in its power "to calm the situation ... it is our duty to restore calm to Nantes, as we wish to do countrywide".

Dozens have been arrested since the riots erupted on Tuesday evening.