Eurostar, the operator of high-speed trains that travel between key European cities, announced on Friday the cancellation of all its services to and from its hub in the French capital.

A spokesperson for France’s national rail operator, SNCF, said the unexploded World War II bomb was discovered during work near the Gare du Nord station.

Services will only be permitted to resume once “mine clearance operations” by the French police are completed, the spokesperson added.

Gare du Nord is a major European transit hub, serving international destinations north of France, such as London; the European Union capital, Brussels; the Netherlands; and the main Paris airport and many regional destinations.

The bomb was discovered about 4am (03:00 GMT) by workers doing earth-moving work near the tracks in the Seine-Saint-Denis region. Minesweepers were sent to the site and their operation is still going on.

Transport Minister Philippe Tabarot expected the disruption to continue for at least the rest of the day.

Bombs left over from World War I and World War II are regularly discovered around France, but it is rare to find them in such a densely populated location.

The repercussions quickly rippled beyond France’s borders. In Brussels, trains to Paris were cancelled until at least Friday afternoon.

“There’s no solution. We’re going to call the hotel and stay one more day and change our train ticket,” Michel Garrot, a retired Parisian visiting the Belgian capital, told The Associated Press news agency.

At London’s St Pancras station, travellers who had been looking forward to Paris’s charms found their plans dashed.

“We’re looking up flights, but our options are limited,” passenger Lauren Romeo-Smith told AP.

In Paris, traveller Kasman Ibrahimi told the Reuters news agency he had planned to catch a train to Cologne, Germany, but would now look for a different route.

French rail operator SNCF said Gare du Nord usually sees 700,000 travellers per day, making it the busiest rail hub in Europe.