German authorities say they have arrested a doctor suspected of radicalizing and financially supporting a man who carried out a suicide bombing in Iraq for the Islamic State group.

Prosecutors and police said the 33-year-old German, whose name wasn't released, was arrested Thursday in Berlin. Officers searched four properties in the capital and Mannheim, his home city, seizing a firearm scope alongside documents and cellphones.

Officials accuse him of radicalizing a mentally disabled 24-year-old German man in Freiburg, where he previously lived, and supplying him with "military articles." They allege the younger man traveled to Syria and Iraq in 2014 after the suspect bought him a one-way ticket, and say he carried out a suicide attack in Beiji last May that killed at least 12 Iraqi soldiers.