France has sought to calm fears that its rail network is under threat from a terrorist attack.

Interior Minister Manuel Valls said French trains, stations and airports are under constant surveillance and no specific threat has been uncovered.

Speaking on French Television Valls said: “We have no evidence which confirms any threat. We have known about these rumours for a number of weeks and we have taken steps. It didn’t involve France directly, it involved a number of neighbouring countries.”

Valls was responding to an article in the German tabloid Bild, which claimed al Qaeda planned to attack either trains, tunnels or tracks in France.

The publication said the information came from the National Security Agency in the United States, which had intercepted an al Qaeda conference call involving the group’s leader Ayman al-Zawahiri.

Germany has since responded to the threat by adopting a series of discreet security measures.

The same call prompted the US to close a number of its embassies across the Muslim world.