Belgian authorities charged three men with terror-related crimes after two days of raids and the detention of 40 people in a major investigation which they said required "immediate intervention" because they feared a new attack was close.

Across Belgium parties were held Saturday to watch live broadcasts of the country's soccer team playing Ireland at the European Championships in neighboring France and some media said such events could have been the targets. Belgium won 3-0 and no major incidents were reported during the game.

Prime Minister Charles Michel said the nation would remain "extremely vigilant, hour by hour," but that the terror level across the nation would remain at the second-highest level, meaning a threat of an attack "is possible and likely." Belgium has been living under such a threat level since the November attacks in Paris, some of whose perpetrators were either Belgian nationals or had lived in Brussels. On March 22, attacks on the Brussels subway and airport killed 32.

"It will be the case in the coming hours that we will take additional and adapted measures," said Michel after a meeting of the nation's security council. He refused to elaborate on the nature of the threat.

The federal prosecutor's office said Saturday that homes and car ports were searched in 16 municipalities, mostly in and around Brussels There were no major incidents during the raids and that no arms or explosives were found.

At first, 40 people were taken in Friday night and early Saturday for interrogation, of which 12 were held. Late Saturday, three Belgian nationals were charged "as perpetrator or co-perpetrator, for having attempted to commit a terrorist murder and for participation in the activities of a terrorist group," a statement said. The nine others were let go.

The government remained on guard after Saturday's actions.

"It is not over. We remain under terror alert 3, it means that something is still up," Interior Minister Jan Jambon said. "Last night, we had a very successful action."

The prosecutor's statement said that "the results of the investigation necessitated an immediate intervention," indicating a violent attack was likely planned in the near future.

The federal prosecutor's office did not link the raids to the March 22 attacks, even though an eighth suspect was arrested as part of the investigation of those attacks late Friday. The Belgian man, identified as Youssef E.A., was charged with "participation in the activities of a terrorist group, terrorist murders and attempts to terrorist murders."

At the same time, four top ministers, including Michel, Jambon and Justice Minister Koen Geens received special protection following unspecified threats.

"We learned about that late yesterday that this close protection would happen. They say there are good reasons for that," Geens said.