"In the lead-up to Christmas, a friendly intelligence service sent a warning to numerous European capitals saying potential bomb or gun attacks could take place in areas with large crowds between Christmas and New Year," Vienna police said in a statement yestrday.
The warning included "several names of potential attackers" but investigations have so far yielded no concrete results, the statement said.
In response to the alert, police officials said they would increase security at public events and tighten controls on roads in Vienna and elsewhere in Austria.