Police in Lower Saxony launched a major raid on Tuesday morning on the organization "German-speaking Islamic Circle", which officials believe to be a "hotspot for the radical Salafist scene".
Around 370 officers took part in the raids beginning at 6am on the nationally active "German-speaking Islamic Circle" (DIK) in Hildesheim. The state interior ministry also placed a ban on the group on Tuesday.
Berlin Christmas market attacker Anis Amri, who killed 12 people in an Isis-claimed terror act in December, had also stayed with the group in February 2016.
According to officials, 'hate preachers' who were part of the group radicalized Muslims and encouraged them to become jihadist fighters in war-torn areas.