Security has been stepped up at police and fire stations across France after a knife-wielding French convert to Islam was shot dead while attacking three police officers.

The assailant, a French national born in Burundi and aged about 20, cried "Allahu Akbar", or "God is great", during the assault, in which the officers were seriously injured.

He'd previously committed petty offences but was not on a domestic intelligence watch-list, although his brother is known for radical positions.