Paris' Gare du Nord train station was evacuated last night as armed police reportedly searched for three "dangerous" terror suspects.

The station was cordoned off at around 11pm local time as armed police poured in and evacuated the site. Passengers were confined to trains, according to witnesses.

According to Le Parisien newspaper, police proceeded to evacuate and search a specific high speed train from Valenciennes, northern France, with 200 people on board.

They were looking for three men that a "partner country" had warned French intelligence last Friday were due to arrive in France where they are suspected of seeking to carry out an imminent attack.

Police surround the Gare du Nord

Since then, there have been reported sightings of the trio in Paris, Bordeaux and Marseille, each time prompting a major police operation - to no avail.

This time, the French capital's daily said, a train conductor and ticket vendor had alerted police to their possible presence.

Unconfirmed reports said two of the men were thought to be Belgian nationals and one Afghan.

The Paris police headquarters later said the "verification" operation was to "dispel any doubt" about a threat.

French police said there was an operation underway at the busy station, which is the terminus of a large suburban and national rail network as well as Eurostar trains from London and Thalys lines to and from Brussels and Amsterdam.

It later gradually began reopening the station early on Tuesday. "End of security checks. Gradual return to normal," Paris police said in a tweet.

Authorities gave no other details about the nature of the operation.

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.

Benjamin, 29, had just got off a train from Lille at 11.15pm when police officers in "classic uniform asked us to leave the station fast".

"As we were going towards the metro, we crossed paths with a more heavily-armed police unit", equipped with bullet-proof shields, he told Le Parisien.

"When we passed by this police unit, people around us started to panic, shout and run towards the metro exits," he is cited as saying.

A Eurostar spokesman 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.

France is under a state of emergency after a string of terror attacks in the last two years left more than 230 dead. The latest occurred on April 20 when an Islamist radical shot dead a policeman on the Champs-Elysées in Paris before being gunned down by other officers.

Security has been particularly tight in the final stages of France's presidential elections, which ended on Sunday with the election of centrist Emmanuel Macron.

11:27PM Operation to 'dispel any doubt' about a threat

The Paris police headquarters said the operation was to "dispel any doubt" about a threat.

11:08PM Police operation 'underway'

11:04PM Police secure outside of the station

10:55PM Reports of security situation inside Gare du Nord in Paris

Hello and welcome to our live coverage of reports that the Gare du Nord in central Paris has been evacuated amid security concerns.

There is a huge police presence inside the station.