A Syrian man charged with war crimes for allegedly participating in the 2013 kidnapping of a United Nations observer has gone on trial in Germany.

The 25-year-old, who came to Germany as a refugee in 2014, is accused of helping guard the observer for the Nusra Front, al-Qaida's branch in Syria. The suspect has been identified only as Suliman Al-S. in line with German privacy rules.

Prosecutors haven't identified the observer but the facts released correspond with those of the kidnapping of Canadian lawyer Carl Campeau, who was abducted from a Damascus suburb. He escaped after eight months.

The Syrian's charges include war crimes, aggravated deprivation of liberty and membership in a foreign terrorist organization. The trial opened Thursday at the Stuttgart state court and will last into next year.