Those targeted in the sweeps were suspected of planning a possible attack in Belgium or of involvement in recruiting for an alleged Chechen terror organization, Belgian officials said. Seven were detained in Belgium's port city of Antwerp, three in Amsterdam and one near the German border city of Aachen.

The arrests were not linked to the recent reports of possible terrorist attacks in Germany, said Judith Sluiter, a spokeswoman for the Dutch National Coordinator for Counterterrorism.

In a second spate of 17 house searches in and around Brussels, "several people" were interrogated in an unrelated investigation into an alleged terror group seeking funds and recruits to go fight in Iraq and Afghanistan, said Leen Nuyts, spokeswoman for the Belgian prosecutor's office.

She refused to be more specific about the number of detentions but insisted the second case had nothing to do with a potential terror attack plot.