German prosecutors say they've have charged a Nigerian man on allegations he was responsible for multiple killings in his homeland as a member of the militant Boko Haram group.

Prosecutors said Friday that 27-year-old Amaechi Fred O., whose surname wasn't released in line with privacy regulations, was arrested Wednesday in southern Germany and charged with membership in a terrorist organization.

Prosecutors allege he joined Boko Haram in 2013, an Islamic extremist group has killed more than 20,000 people in its nine-year insurgency.

He is accused to have been part of four attacks on Nigerian civilians during his year with the group, including two on schools and one on a village where he allegedly "killed multiple people himself."

It wasn't immediately clear when he came to Germany.