The United States Government is to issue a new travel alert for American tourists in Europe.Travellers will be told to be vigilant while travelling because of what have been described as credible threats from Al Qaeda.
Security agencies have suggested that there are plans to mount attacks in European cities similar to those in Mumbai in November 2008.
Tourists are to be warned to stay away from crowded places.
There was no immediate indication when the alert might be issued.
News media in the last week reported that western intelligence agencies had uncovered an Al Qaeda plot to launch attacks in Britain, France, Germany and the United States.
The reports said well-armed, commando-style teams of jihadists planned to seize and murder Western hostages in a manner similar to the Mumbai attacks of 2008.
Two Indian hotels in Mumbai were besieged by 10 gunmen who killed 166 people and injured more than 300.