Police arrested two men “suspected of planning an attack” in Belgium after house searches during raids late Friday, federal prosecutors said on Saturday.

The two, named as 33-year-old Nourredine H. and his brother Hamza H., will appear before a judge to determine whether they should be held in custody beyond an initial 24 hours.

Belgium has remained on high alert following deadly March bombings claimed by ISIS in Brussels and a wave of deadly attacks in the last month in France and Germany.

The country, which is home to European Union institutions and the headquarters of NATO, is on a security alert level of three out of a maximum of four, a “serious” status with a “possible and probable” threat.

“Based on provisional results from the investigation, it appears that there were plans to carry out an attack somewhere in Belgium,” the federal prosecution office said in a statement.

For the time being there was no connection with the attacks at Brussels airport and the metro on March 22, in which 32 people were killed, the prosecution office said.

Police carried out seven house searches in the French-speaking region of Mons and a further house search in Liege. No weapons or explosives were found.

The searches were carried out at the request of a magistrate specializing in terrorism investigations, the statement said.

Belgian authorities last month charged two men with terrorist offences amid reports of a planned attack on a Euro 2016 fanzone in central Brussels.

Belgium then beefed up security for its July 21 national day celebrations after the truck attack that killed 84 people in the French city of Nice on Bastille Day, July 14.