BRUSSELS — Two people have been arrested in Belgium on suspicion of planning attacks in Brussels during the holidays, the federal prosecutor’s office said today.

The investigation revealed “the threat of serious attacks that would target several emblematic places in Brussels and be committed during the end-of-year holidays,” the prosecutor’s office said.

A source close to the investigation said the Belgian capital’s main square, thronged this time of year with holiday shoppers and strollers, was one of the suspected targets.

“On the Grand Place, there are a lot of people, as well as soldiers and police who are patrolling, as well as a police station nearby,” said the source. The two suspects, who the source said were male, were arrested following searches Sunday and Monday in the Brussels area, the Liege region and Flemish Brabant, the prosecutor’s office said. It did not disclose their names or further information about them.

One was charged with acting as the leader and recruiter of a terrorist group planning to commit terrorist offenses, the other with participating in a terrorist group’s activities as a principal actor or co-actor, the prosecutor’s office said.

During the searches, military-type training uniforms, propaganda materials from the Islamic State group and computer material were seized and are being examined. However, no weapons or explosives were found, the prosecutor’s office said.

Six people were taken in for questioning, but four were released, the office said.

The prosecutor’s office said no additional details would be made public, but that the probe was not connected to the Nov. 13 attacks in Paris, in which numerous suspects, including presumed ringleader Abdelhamid Abaaoud and fugitive Salah Abdeslam, had connections to Belgium.

On Nov. 21, after the Paris attacks that killed 130 and injured hundreds, the terrorist alert level for all of the Belgian capital was temporarily raised to its maximum level.