The operation Friday into Saturday included searches of dozens of houses, according to a statement from the prosecutor's office.
The searches were spread through 16 municipalities.
"The investigatory results necessitated an immediate intervention," the prosecutor's office said. "The investigation continues. In the interest of the investigation, currently no further details can be given."
Belgian state broadcaster RTBF reported Saturday that the overnight raids were made after messages were intercepted indicating attacks were being planned. The possible targets were places where Belgian football fans congregate to watch Euro 2016 games.
Belgium won Saturday's match against the Republic of Ireland 3 to 0.
The prosecutor's office said no further information could be released concerning the seized items or the identities of those arrested. A judge will decide on their possible detention Saturday.
No arms or explosives had been found in the overnight raids, the office added.
Ministers get extra protection
Ahead of the raids, several senior ministers were given heightened security protection because of new intelligence about specific threats. according to RTBF, which cited the government's Coordinating Unit for Threat Analysis.
Prime Minister Charles Michel, Foreign Minister Didier Reynders and Interior Minister Jan Jambon are among those receiving heightened protection, RTBF reports.
Belgian officials have been grappling with terror investigations. In March, twin bombings struck the Brussels airport and a metro station, killing 32 people
. ISIS claimed responsibility for the attacks.
Belgium has not raised the overall threat level, but has a reason to crack down on terrorism.
Per capita, it has the highest number of foreign fighters
in Syria of any Western European nation.