Seven people suspected of supporting ISIS and plotting a "terrorist attack" were arrested in Belgium on Thursday, prosecutors said.
Three of the suspects hold Belgian nationality and almost all are ethnic Chechens, prosecutors said in a statement.
"The exact target of the planned attack has not yet been determined," they said.
Police backed by elite units raided nine addresses in several towns in western Belgium in an operation led by an investigating judge specialised in terrorism cases.
The judge will decide "at a later stage" if there is enough evidence to charge the suspects, the prosecutors said.
"Possible charges are attempted terrorist assassination, participation in the activities of a terrorist group and preparation of a terrorist attack," they said.
Prosecutors said that all seven arrested were "suspected of preparing a terrorist attack in Belgium".
They all "belong to a group of strong supporters" of ISIS.
A spokesman for the federal prosecutors' office, Eric Van Duyse, told AFP that "they apparently intended to target an institution located in Belgium" and had been "actively searching for weapons".
The police raids took place in the city of Ghent and the smaller towns of Roeselare, Menen, Ostend and Wevelgem.
ISIS claimed responsibility for suicide bombings in Belgium on March 22, 2016, at Brussels airport and the capital's metro, killing 32 people and wounding hundreds.
Those bombings occurred months after the November 2015 attacks in Paris that were planned by the same ISIS cell and which killed 130 people.
Chechnya, a republic in Russia's North Caucasus region, is ruled by pro-Kremlin strongman Ramzan Kadyrov.
Mr Kadyrov supports Russian President Vladimir Putin's war in Ukraine and has sent his militia there to fight.
