Authorities closed two main railway stations and have since said they've uncovered intelligence suggesting up to seven suicide bombers planned to target the city.
New Year's Eve festivities were also cancelled on the Champs-Élysées in Paris.
While in Brussels fears of a terrorist threat led to the city's traditional fireworks being called off.
Six people were arrested by police in the Belgian capital who discovered a bomb plot targeting last night's celebrations.
Three of the six have now been released.
