Prosecutors have indicted a German man accused of joining the Islamic extremist group al-Shabab in Somalia on terrorism charges.

German federal prosecutors said Tuesday that the indictment against the 28-year-old identified only as Abshir Ahmed A., in line with German privacy rules, was filed Sept. 12 at a Frankfurt court. The suspect was arrested at Frankfurt airport as he returned home in July.

The charges include membership in a foreign terrorist organization and violation of weapons control laws.

Prosecutors say the man is believed to have joined al-Shabab in Somalia in 2012, undergoing weapons training and then being deployed in a defensive position for the group. They say that health problems forced him out of that posting.

Al-Shabab is waging an insurgency against Somalia's weak western-backed government.