Traffic at the Paris Gare du Nord train station was halted on Friday after a World War II bomb was found on tracks leading to France's busiest terminal, officials said. Police are working to disable the device.

The unexploded bomb was found "in the middle of the tracks" overnight during maintenance work carried out in the area of Saint Denis suburb, the national SNCF rail company said.

The bomb "dated to the Second World War", the RER B suburban train wrote in a post on X.

SNCF said in a statement that traffic would be stopped at the train station, which hosts Eurostar trains as well as high-speed and local services, until mid-morning at the request of police. 

“We invite travellers to postpone their trip,” it said. 

The Gare du Nord train station lies in the north of Paris and is the country's busiest rail terminal, serving an estimated 700,000 people each day, according to the SNCF.

Bombs left over from World War I or World War II are regularly discovered around France but it is very rare to find them in such a people-packed location.