BRUSSELS  In a series of early morning raids, the police in three European countries arrested 11 people on Tuesday, saying that some were part of an international jihadist group planning a terrorist attack in Belgium and that others were members of a Chechen group.

Belgian television showed pictures of arrests by police officers in two areas of Antwerp, a port city with a large immigrant population, where 7 of the 11 people were detained.

Three arrests were made in Amsterdam, and one in Aachen, near Germany’s border with Belgium.

The suspects were Belgian, Dutch, Moroccan and Russian of Chechen origin, said Leen Nuyts, a spokeswoman for the Belgian federal prosecutor’s office.

The German authorities said the suspect arrested in Aachen was 31 and of Russian origin. They said he would be transferred to Belgium.