Vienna police warns of terror attacks on European capitals

Police in the Austrian capital of Vienna have stepped up security around the city after a warning to several European capitals about a possible terror attack between Christmas and New Year.

The police said that the warning, about a gun or bomb attack, did not specify any targets and that authorities in Vienna did not intend to cancel any specific events.

"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," Vienna police said in a statement.

"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.

The police have asked Austrians for their understanding of the need for more security controls.

City authorities said they would increase surveillance of places where crowds are expected to gather, including transport hubs, and pay closer attention to suspicious bags or suitcases.