BERLIN – German police on Friday arrested three suspected members of al-Qaida who officials say posed a “concrete and imminent danger” to the nation.

Authorities did not say whether the suspected terrorists had planned specific targets and offered few details, but security officials said that all three were of Moroccan origin. They also said that two were arrested in the western German city of Duesseldorf and one in nearby Bochum.

There was no indication the arrests had any link to Thursday’s bombing in Morocco that killed 15 people in a crowded tourist cafe.

Germany has escaped any large-scale attack by an Islamic terror organization, such as the Madrid train bombings of 2004 and the London transit attacks of 2005. But Germany’s presence as part of the NATO coalition in Afghanistan has sparked anger, and at least two major plots have been thwarted or failed in Germany before they could be carried out.