The action followed clashes between demonstrators and police on U.S. campuses and a blockade at Paris's Sciences Po university
The hooded shooter reportedly fled the spot after opening fire around 9:50pm local time on Friday night.
Armed police have sealed off roads near the city centre and are working to apprehend the gunman.
A 14-year old boy has allegedly been shot in the leg, while two other youths have been injured.
According to French news site La Voix Du Nord, those injured had been shot several times.
Though the motive for the attack has yet to be verified, French media reports cite police as saying the incident is not terror-related.