Celle - A teenage girl went on trial in Germany Thursday for stabbing a police officer, an assault allegedly "ordered" by the Islamic State organisation but which was not claimed by the jihadist group.The court in the northern city of Celle ruled at the start of the proceedings against Safia S, 16, that they would take place behind closed doors because she is a minor."The defendant must be protected from further exposure and the accompanying stigmatisation," presiding judge Frank Rosenow said.The German-Moroccan national risks 10 years in prison for "attempted murder, grievous bodily harm and support for a foreign terrorist organisation".She entered the courtroom wearing a beige headscarf and fashionable eyeglasses and spoke clearly and confidently to the judge.Prosecutors said the teenager, who is believed to have been radicalised as a young girl, had sought to catch the attention of police officers by following them around at the main train station in the northern city of Hanover.As the officers called her over for an identity check, Safia S allegedly stabbed one of them in the neck with a vegetable knife before being overpowered by another officer.The teenager was already known to police before the February 26 attack as she had sought to travel to Syria to join ISIS fighters a month earlier.Her mother flew to Istanbul to bring her home and as they landed back in Germany, Safia S was taken away by police and interrogated over her botched attempt to reach the war zone.Her mobile phone was also seized, but it was not until after the stabbing assault that investigators translated the Arabic messages on the phone - which had instructed her to commit an "act of martyrdom".'Radicalised as a child' A German-Syrian man, 20, Mohamed Hasan Kharsa, went on trial with Safia S for failing to report her plans to police, even though he was aware that she was plotting to attack a police officer.The young man had sought to flee Germany but was arrested in Greece and extradited on Tuesday.Safia S was apparently already radicalised as early as 2008. At that time, when she was just seven or eight years old, she had appeared in an online video by Pierre Vogel - a notorious Salafist preacher in Germany.But it was only in November 2015 that she pledged allegiance to the ISIS, investigators said.Her brother had also sought to join the jihadist group in Syria but was arrested and jailed in Turkey, according to news agency DPA.Meanwhile on Thursday, a Syrian man went on trial in the southwestern city of Stuttgart accused of being among jihadists who kidnapped a UN peacekeeper in Damascus in 2013 in what prosecutors call a "war crime".The 25-year-old accused, named only as Suliman A-S, is believed to be a member of a branch of the Al-Nusra Front jihadist group.He allegedly participated in the abduction on February 17, 2013 and was "involved in guarding the kidnapped victim between March and June 2013".Jihadist attacksHe is "suspected of an attack during Syria's civil war against a person, who was involved in a peacekeeping mission under the United Nations Charter, and was therefore entitled to protection," the federal prosecutor's office said when he was arrested in January.A verdict is not expected before April 2017. Germany has so far been spared large-scale jihadist attacks.But Europe's biggest economic power has been shaken by two assaults claimed by the ISIS and carried out by Syrian asylum seekers - an axe rampage on a train in Wuerzburg that injured five, and a suicide bombing in Ansbach in which 15 people were hurt. Police last week said they had foiled an alleged plot by a Syrian refugee to bomb one of Berlin's airports.The cases have fuelled anxiety over Germany's record influx of nearly 900 000 refugees and migrants in 2015.