PARIS (Reuters) -A teacher was killed and several people injured in a knife attack in a school in the northern France city of Arras on Friday, BFM TV said.

Local police confirmed there had been a knife attack. Regional authorities said the attacker had been arrested.

Police could not confirm media reports that the assailant had shouted 'Allahu Akbar'.

Citing a police source, BFM TV reported the attacker was about 20 years old and could have been a former pupil. It said the attacker's brother was also arrested.

BFM TV said the person killed was a French language teacher, while a sports teacher was stabbed and injured.

Pupils were confined to their classroom, it said.

French interior minister Gerald Darmanin said a police operation was underway in a school.

(Reporting by Michel Rose, Charlotte Van Campenhout, Tassilo Hummel Writing by Ingrid Melander; editing by Richard Lough)