Emergency services rushed to the scene after a “suspicious vehicle” was spotted near the port’s car ferry terminal, Lille-based newspaper La Voix du Nord reports.
A source told French radio network France Info the driver of the car had threatened to blow himself up along with his vehicle.
Explosives experts were dispatched to the scene and a security cordon put in place shortly after 1pm local time (noon BST).
Witnesses reported hearing an explosion at around 2.30pm local time (1.30pm BST) as the suspect device was destroyed in a controlled blast.
Pictures from the scene show the suspect vehicle – a black VW car – stopped at a security checkpoint.
France Info reports the driver arrived at the ferry terminal without a ticket or identity papers and demanded to speak to French President Emmanuel Macron as well as King Mohammed VI of Morocco.
The driver was arrested and the lockdown lifted at around 3pm local time (2pm BST).
Long tailbacks have formed on the A16 motorway after traffic was prevented from entering part of the port.
More to follow…