Anti-Israel protest in Belgium (file)
Anti-Israel protest in Belgium (file) Flash 90

The European Commission said Sunday it has not been told of any specific threat against it, after reports suggested its Brussels headquarters was a possible target for jihadist fighters returning from Syria.

Belgian authorities confirmed to AFPSaturday they had made several arrests as they sought to prevent jihadist fighters or sympathizers with the Islamic State terrorist organization from carrying out attacks.

There was no visible increase in external security around the Commission headquarters in the European Union district of central Brussels early Sunday.

"The Commission has not received any information about specific threats," a Commission spokesman said, adding that all further enquiries should be directed to the local authorities.

A spokesman for the federal judicial office in Brussels said he could not comment on the matter.

Dutch public broadcaster NOS said Saturday at least two people among those arrested in the Belgian operations came from The Hague.

Citing unnamed sources, NOS said one possible target was the Commission building, with the aim being to kill as many people as possible, similar to an attack in May on the Jewish museum in central Brussels which left four dead.

The suspect in that case, Frenchman Medhi Nemmouche, spent more than a year fighting with Islamist extremists in Syria as an ISIS torturer and is now being held in Belgium on charges of murder in a terrorist context.

The Commission is the public face of the European Union and it has one of the most high-profile buildings in Brussels, housing several thousand officials and the top brass in charge of the daily running of the 28-nation bloc.

Brussels is also home to NATO's headquarters and many other international companies and organisations, but security is mostly low-key and discreet.

Belgium, like several European countries, is increasingly worried about its nationals going to fight in Syria and Iraq for fear they will return home battle-hardened and even more radicalized, posing a threat to security.

It is estimated some 400 Belgians may have done so, while about 90 have returned home.

"Our starting point is that among them, one out of nine aims to carry out an attack," L'Echo daily reported Saturday, citing an unnamed source.