German prosecutors said Thursday that they have charged a German-Algerian dual national with supporting a terrorist organization over allegations that he aided ISIS militants in Syria and Iraq. The federal prosecutors office said that 32-year-old Samir K. was arrested Wednesday in Baden-Wuerttemberg after a series of searches in the southwestern state, as well as in Brandenburg, Hamburg and Lower Saxony. Prosecutors said K., whose last name wasnt released in line with privacy laws, organized email, Telegram, Twitter, WhatsApp and Facebook accounts under aliases for four ISIS militants between the years 2015 and 2017. Using the accounts, prosecutors said, the militants from Germany were able to maintain "comparative communication" with other members of ISIS and distribute messages on the internet. K. is being kept in custody as the investigation continues. German security officials have been on high alert since rejected Tunisian asylum seeker Anis Amri killed 12 people by plowing a truck in a Christmas market in Berlin in December 2016. The attack exposed flaws in how Germany’s surveillance agencies work and heightened fears that militants entered Germany after it opened its borders in 2015 to more than a million people seeking asylum.