German citizen Marius A. is alleged to have travelled to Syria in 2013 to fight with the Al-Qaida splinter group, while three other men are accused of collecting funds on his behalf.
Four men have been indicted in Germany on suspicion of supporting the Islamic extremist group Jabhat al-Nusra, prosecutors said on Thursday.
One of the men, all of whom were indicted last month, is also understood to be a member of the jihadist organisation.
Jabhat al-Nusra was originally the Syrian branch of Al-Qaeda, formed to fight forces under Bashar al-Assad in the Syrian Civil War.
It later broke away but remains active as part of a Salafist alliance seeking to establish an Islamic state in Syria. The group was blacklisted by the United Nations in 2013 after being designated a terror group by the United States the previous year.
Prosecutors said a German citizen, named only as Marius A., was believed to have travelled to Syria in October 2013 to join al-Nusra and remained a member until March 2014.
He reportedly received firearms training and took part in fighting at least once, also receiving funds for the group in Turkey.
Separately German-American citizen Maher M., German-Algerian citizen Mohamed S. and German-Spanish-Moroccan national Avid E.G.M. are accused of collecting funds for al-Nusra at Marius A.’s request. They were said to have transferred him the money in late 2013 or early 2014.
Marius A. was detained in Senegal last September and extradited to Germany in May. He is still in custody.