The European Commission was among possible targets for jihadist fighters returning from Syria, reports said Saturday, as the Belgian authorities cracked down in an effort to thwart extremist attacks.

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

“They were planning an attack. One of the targets was the European Commission building” in Brussels, known as the Berlaymont building, NOS reported, citing unnamed sources.

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“Individual commissioners were not particularly targeted. It would be more like the Jewish museum attack… with the aim to kill as many people as possible,” it added.

The suspect in the attack on the Jewish museum in central Brussels in May, which left four people dead, is Frenchman Mehdi Nemmouche who spent more than a year fighting with Islamist extremists from the Islamic State in Syria and is now being held in Belgium on charges of “murder in a terrorist context”.

Earlier Saturday, Belgian authorities said they prevented several attacks by jihadist fighters returning home from Syria and by sympathizers with the Islamic State.

Up to 400 Belgian nationals are estimated to have gone to fight in Syria, with about 90 known to have returned home, L’Echo said.

Several arrests have been made, according to the report.

“Our starting point is that among them, one out of nine aim to carry out an attack,” a source said. “That is a conservative estimate, if you also take into account the people who help them.”

“We are working full time on the problem of the returning fighters,” Belga news agency cited a federal judicial spokesman as saying.

“We work together with the security services and that led us to carry out several operations,” the spokesman said.