The terror alert was handed to Austrian police this evening from a "friendly" intelligence service, as evidence grows that terrorist cells are planning to hit Western targets.

It has prompted police across the continent to increase security measures in a bid to prevent a Paris-style copycat attack on an unknown location in Europe.

The warning made specific mention of the threat to shoppers and revellers in “crowded spaces” and warned that the strike could take place between Christmas and New Year.

A statement released by police in Austria said: "In the days before Christmas a warning was sent out by a friendly (intelligence) service to numerous European capitals, saying that it could come to an attack involving explosives or a shooting between Christmas and the New Year in crowded spaces."

It added: "Several possible names of potential attackers were mentioned, which were checked, and the investigation based on (these checks) has so far yielded no concrete results.”

A spokesman for the Interior Ministry of neighbouring Germany said: "Germany is still in the crosshairs of terrorism.”

The warning comes on the same day that shoppers were told they could be targeted by terrorists.

Will Geddes, head of global security firm International Corporate Protection, said those seeking out Boxing Day sales were a likely target.

He said: “I don't think Christmas Day will be a target for ISIS, even though it's a Christian holiday, because there won't be big crowds which is what they want for maximum impact.

"But Boxing Day could be as lots of people will be out for the sales in cities across the UK, all gathered in big crowds." ,Express reported.

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