BRUSSELS: Seven people were imprisoned in Belgium Wednesday in two investigations into "possible terrorist attacks", the federal prosecutor's office said.

The seven, five Belgians as well as a Turk and a Bulgarian, were charged with participation in the activities of a terrorist group.

Five of them were also charged with "preparation of a terrorist offence", the prosecutor said.

Raids were conducted late Monday on homes in the capital Brussels, the port city of Antwerp and the border town of Eupen, the federal prosecutor's office said on Tuesday.

'Operations under way' in Belgium linked to 'terrorist threat': police

Eight were arrested in the raids, but one of the suspects arrested in Antwerp has since been released.

These were in relation to two inquiries -- one led by federal police in Brussels and the other by an investigating magistrate in Antwerp.

The parallel investigations triggered a raid in Molenbeek, an inner-city Brussels district that has been the focus of some previous terror probes.

More details of the potential targets of these attacks have not yet been released.

The investigations in Antwerp and Brussels had initially focused on "two young adults suspected of violent radicalism", state broadcaster RTBF reported.

The country's biggest ever criminal trial of nine suspects accused of taking part in the March 2016 suicide bombings that killed 32 people is underway in Brussels.