French intelligence services are tracking the authors of a message apparently describing a militant threat against the Eiffel Tower, the daily Le Monde said on Friday.
The newspaper said Portuguese air traffic authorities had intercepted a "vague and confused" short wave radio message apparently describing a threat on Thursday, but were not "panicked" by the message, according to a police source.
The French capital is already at its second highest security alert level and further public security measures would serve little purpose, Le Monde quoted police as saying.
"We've been at red for several months. It's the highest level before scarlet alert which is implemented when there are attacks," the local police headquarters told the newspaper.