The suspect in the attack, which left three people dead and a person critically injured, is believed to have trained with foreign backed terrorist groups in Syria.

The European Union's governments agree they should monitor suspected foreign backed terrorists with Syrian combat experience who enter Europe, exchange information on violence-prone militants more quickly and step up cooperation between intelligence services, diplomats said.

The militants should also be prohibited from travelling to Syria "within the limits of legal possibilities," German Interior Minister Thomas de Maiziere said. He wants plans for a controversial European system to share air passenger information to be revived too.

Decisions are not expected until early July.

"The abstract danger of the threat from foreign militants has become a concrete danger in a neighboring state, and we have to draw all consequences from this," de Maiziere had said before meeting his EU counterparts in Luxembourg.

The suspect in the Brussels shooting, continues to be held in France after a court decided Thursday to postpone until June 12 a decision on his extradition to Belgium.

De Maiziere and his Austrian counterpart, Johanna Mikl-Leitner, said it was necessary to tackle the root causes of radicalization.

EU Counter-Terrorism Coordinator Gilles de Kerchove said that youths with low levels of schooling who are looking for adventure are especially at risk.

He estimates that more than 2,000 Europeans have been to war-torn Syria, are headed there or have returned.

The Luxembourg talks came hours after Group of Seven (G7) leaders meeting in Brussels pledged to "intensify our efforts to address the threat" of Syria returnees.

British Prime Minister David Cameron said Thursday extremism and terrorist groups abroad are the "greatest threat that we face."

The group of leading industrialized nations also includes Canada, France, Germany, Italy and Japan.

NJF/NJF