The two men were detained in two different towns in Belgium, Verviers and Tournai, spokesman for the prosecutor's office, Eric van der Sypt said on Saturday.
He declined to say why the raids were carried out. No weapons, explosives or other dangerous materials were found during the operations overnight, van der Sypt added.
The RTL news service, citing unnamed sources, said on its website that the man detained in Verviers was planning an attack on fans watching Belgium's next Euro 2016 game against Hungary on Sunday.
Van der Sypt stated that the new raids had no connection to the March 22 terror attacks on Brussels airport and on the city's metro system which killed 32 people or on those in Paris in November that left 130 people dead. Both attacks were claimed by the terror organization "Islamic State" (IS).
Last Saturday, Belgium charged three men with "attempted terrorist murder" after massive anti-terror raids linked to a reported threat to fans during Euro 2016.
Police initially detained 40 people in the raids last week in Brussels and across Belgium but found no arms or explosives.
Subsequently, Belgian Prime Minister Charles Michel promised "additional and updated security measures" and stressed that public events would go ahead as planned. "We want to continue living normally," he added.
