General view of the exterior of the Gare du Nord train station in Paris
General view of the exterior of the Gare du Nord train station in ParisReuters

Police evacuated the Gare du Nord station in Paris for several hours overnight Monday, evacuating passengers from platforms and sealing off the area over an unspecified security threat, reports The Associated Press.

Paris police spokeswoman Johanna Primevert was quoted as having said that the operation was aimed at "removing doubt". She would not say what prompted the operation or whether there had been any injuries or arrests.

By 2:00 a.m. local time, police gradually began reopening the station, Reuters reported.

An eyewitness at the scene told the news agency there were between 20 to 30 police vans outside the station, and that officers were wearing balaclavas and carrying assault weapons.

"End of security checks. Gradual return to normal," Paris police said in a tweet.

The busy station is the terminus of a large suburban and national rail network as well as Eurostar trains from London.

A Eurostar spokeswoman said the incident did not appear to have any relation to its trains and did not appear to affect its passengers.

The operation began after the last Eurostar arrivals and departures late Monday, according to AP.

Dozens of police officers and transport staff surrounded the large station in northeast Paris and sealed off all roads leading in as local residents milled around, the news agency said.

France has been rocked by a wave of deadly jihadist attacks which began on January 2015 and remains on high alert.

In late April, a terrorist murdered a police officer in an attack at the Champs Elysees in the French capital. The attack was later claimed by the Islamic State (ISIS) terrorist group.

In April, French security services arrested two men accused of plotting an attack.

The previous month, French authorities arrested four members of a family as part of a preliminary investigation in connection with a plot to carry out an attack.