Dozens of anti-terror raids were carried out across Belgium overnight in a case that needed “an immediate intervention,” and 12 people suspected of planning new attacks were arrested, federal prosecutors and reports said Saturday.

The raids took place in 16 communes in Brussels, Flanders and Wallonia during which about 40 house searches were carried out, the prosecutors said in a statement.

The raids “passed off without incident,” they said, adding that “until now no arms or explosives were found.”

“Forty persons were taken in for questioning. Twelve among them were arrested. The investigating judge will decide on their possible detention later today,” it said.

“152 garage lockups were searched as well,” it said, adding: “Currently no further information can be given concerning the seized items or the identities of the arrested persons.”

Europe is on high alert as the Euro 2016 soccer tournament is under way in neighboring France. Suicide bombers killed 32 people in Brussels in March following attacks in Paris in November in which 130 people died.

Investigators have confirmed links between the perpetrators, some of whom were based in Belgium.

Flemish public broadcaster VTM said the people arrested overnight were suspected of planning an attack in Brussels this weekend during one of Belgium’s soccer matches in the Euros.

Belgian police on Wednesday received an anti-terror alert warning that a group of ISIS fighters recently left Syria en route for Europe planning attacks in Belgium and France, security officials said.

On Friday police arrested and detained a man named as Youssef E.A, a Belgian national, on suspicion of taking part in terrorist activities in connection with the Brussels attacks.

Belgian media also reported that four top ministers, including Prime Minister Charles Michel, have received special protection following unspecified threats. The news could not immediately be confirmed.