THE HAGUE, July 16(Reuters) - A Dutch court sentenced a 49-year-old Syrian man on Friday to 20 years in prison for war crimes over his role in the execution of a government soldier during Syria"s civil war. Judges said Ahmad al Khedr, also known as Abu Khuder, was a member of the Nusra Front rebel group, at one point al Qaeda"s affiliate in Syria. They concluded his voice could be heard in a video of the execution of a captured and bloodied Syrian soldier who was shot on the banks of the Euphrates river in 2012. "Executing an imprisoned foe by the accused is not only murder but also an egregious violation of the written and unwritten rules of international humanitarian law and universal human rights," the judges wrote in their 40-page verdict. The case against Al Khedr was brought under Dutch universal jurisdiction laws under which national courts can try suspects for war crimes, crimes against humanity and genocide committed on foreign soil as long as the suspects reside in the Netherlands. Al Khedr has been in the Netherlands since 2014, where he had been granted temporary asylum. The charges against him were based on witness testimonies provided by German police, Dutch authorities said. It is the third time a Dutch court has convicted a Syrian national of war crimes during the civil war, previously handing down prison terms of up to seven years. Al Khedr"s sentence was more severe than those of previous cases with Syrian fighters because he was found to have personally participated in the execution. In the absence of a tribunal for atrocities in Syria, where a decade of civil war killed an estimated 400,000 people and drove millions more from their homes, European courts have tried a handful of suspects. But most alleged violations have gone unpunished.