PARIS — Police poured into Paris' Gare du Nord station late Monday (May 8), evacuating passengers from platforms and sealing off the area in a new security scare to hit the French capital.

Paris police spokeswoman Johanna Primevert told The Associated Press that the operation was aimed at "removing doubt" but would not say what prompted it or whether there had been any injuries or arrests. A station employee said the operation focused on a train from Valenciennes in northern France. French paper Le Parisien reported that police were looking for three "dangerous" suspects who may have arrived in Paris.

At 7.51am, Singapore time, local police tweeted that the operation was over and the situation was gradually returning to normal.

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

France is under a state of emergency imposed after a series of Islamic extremist attacks. The operation came the day after a tense and closely watched presidential election that was won by independent Emmanuel Macron. He has said one of his top priorities will be ensuring France's security.

Police started pouring into the station just after 11pm and asked where the train from Valenciennes was, according to a station employee, who was not authorised to be publicly named. Station staff directed officers to platform 10, where they were quickly joined by more and more police. Within minutes, authorities began evacuating the entire station, the employee said.

By 1.30am, the operation appeared to be winding down, with police on the outskirts of the cordon around the station beginning to pack up and the cordon was gradually pared back.

Paris - Évacuation de la Gare du Nord, gros dispositif sur Place et arrivée à l'instant de la BRI. pic.twitter.com/TMceSIJwIn — Remy Buisine (@RemyBuisine) May 8, 2017

Mr Dave James Phillips, a 39-year-old technology consultant from Britain, said he was getting off the last train in from London when he saw officers flooding the station.

"There were police immediately, and a chap with his hand on his gun," Mr Phillips told AP. "As we were walking down the platform, one came down and said, `Rapide, rapide. Out, out'.''

Mr Phillips said police kept pouring into the station as passengers were hustled out and police buses and unmarked cars were ``driving quite dramatically up the road.''

Mr Phillips said he had since left the area.

"Hopefully nothing happened,'' he said.

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.