Police have detained eight people during investigations into an alleged terrorist plot in Belgium, federal prosecutors said on Tuesday.
Raids were conducted late on Monday on homes in the capital Brussels, the port city of Antwerp and the border town of Eupen.
Prosecutors said that at least five of those detained were suspected of planning to “commit a terrorist attack in Belgium”.
The target of the attack was not identified.
A judicial source told AFP those arrested were “very young radicalised people” suspected of belonging to an extremist movement.
The prosecutor cited two inquiries, one led by federal police in Brussels and the other by an investigating magistrate in Antwerp.
Both led to house raids on Monday.
“There are links between the two files, but further research will have to show to what extent the two groups were intertwined,” prosecutors said.
The Antwerp inquiry led to five arrests, including one in Eupen near the German border, and the Brussels probe led to three arrests.
In both cases the suspects have been detained but not yet charged.
The parallel investigations triggered a raid in Molenbeek, an inner-city Brussels district with a large North African population that has been the focus of previous terror probes.
The investigations in Antwerp and Brussels initially focused on “two young adults suspected of violent radicalism”, state broadcaster RTBF reported.
Between 2016 and 2018, Belgium faced a wave of deadly extremist attacks.
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 under way in Brussels.
The bombings were carried out by the same extremist cell that killed 130 people during the November 2015 attacks in Paris, helping with planning from hideouts in Belgium.
Monday's arrests mark the first such terror inquiry to be made public in Belgium since November, when a Brussels man was charged with terrorism offences after stabbing a police officer to death.
Officials had however warned of the continued danger.
The threat of terrorism “still remains, with planned attacks that are regularly prevented by our services”, Belgian federal police chief Eric Snoeck told RTBF on Friday.
In its latest annual report published in January, Belgium's domestic intelligence service noted “a worrying rise in the number of increasingly young people falling into extremist radicalisation” of a religious and politically extreme nature.
The OCAM national threat analysis centre said on Tuesday that Belgium's terror alert level would remain at “medium”, or a level of two out of a maximum of four.
Agencies contributed to this report
