Police on Saturday said a “friendly” intelligence service has warned European capitals of the possibility of a shooting or bomb attack before New Year’s, prompting police across the continent to increase security measures.

“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, which came about six weeks after at least 130 people were killed in an Islamist bombing and shooting attacks in Paris.

“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.”

Police asked Austrians for their understanding of the need for more security controls.

Extra steps include surveillance in crowded spaces, “especially at events and traffic hubs,” as well as intensive identity checks and a higher alertness for objects that could conceal explosives, such as bags and bicycle frames, it said.

Vienna police were not immediately available to comment.

A spokesman for the German Interior Ministry said it does not comment on particular situations for operational reasons.

“Germany is still in the crosshairs of jihadist terrorism,” he said, adding that the country had reviewed and, where necessary, adapted security measures.

Meanwhile, in Brussels, a police commission is interviewing staff at a college there after education authorities failed to act on concerns that a student who later became one of the Paris suicide bombers had been radicalized, two Belgian newspapers said Saturday.

Bilal Hadfi, 20, named as one of the attackers who detonated a suicide bomb outside the Stade de France in Paris on Nov. 13, attended the Anneessens-Funck college in Brussels until he dropped out in February to travel to Syria.

The Belgian Dutch-language newspapers De Morgen and Het Laatste Nieuws cited documents that they said showed staff members had serious concerns about Hadfi’s extremist views, which were evident in the classroom.

The reports did not elaborate on the exact nature of the documents but said they showed that the college director informed the Brussels education board in April that Hadfi, a French national, had traveled to Syria.

“Committee P” (le Comite Permanent de Controle des Services de Police), as the Belgian police-oversight authority is known, is investigating why the information was not passed along to police, the newspapers said.

No representatives of the college, Committee P or Brussels education board were immediately available to comment.