A court in Russia halted the trial of a 20-year-old Ukrainian man charged with abetting terrorism shortly after it got under way, sending the case back for additional investigation.
Pavlo Hryb, who denies the charge and whose family contends he was set up by the Russian Federal Security Service (FSB), went on trial at the North Caucasus Regional Military Court in Rostov-on-Don on July 23.
But the court said it found that the formal charge against Hryb was based on a clause of the Criminal Code that had not been in place at the time of the alleged crime.
There was no indication that Hryb would be released from custody.
Hryb pleaded not guilty after he hearing began, saying that "critical mistakes have been made during the investigation."
Hryb went missing in August 2017 after he traveled to Belarus to meet a woman he met online.
Relatives believe he walked into a trap set by the FSB, which later told Ukraine that Hryb was being held in a detention center in Russia on suspicion of abetting terrorism.
Russian investigators accuse Hryb of using the Internet to instruct a teenage girl in Russia's southern city of Sochi to carry out a terrorist act using an explosive device.
Hryb's father, Ihor Hryb, has argued that the case against his son was Russian retaliation for Internet posts that were openly critical of Russia's interference in Ukraine.
Russia seized control of Ukraine's Crimean Peninsula in March 2014, after sending in troops and staging a referendum dismissed as illegal by at least 100 countries. Moscow backs separatists in a war against government forces that has killed more than 10,300 people in eastern Ukraine since April 2014.
The Ukrainian Foreign Ministry has condemned what it called Russia's "persecution of Ukrainian citizens in Russia and elsewhere, groundless detentions of Ukrainians, violation of their rights to have fair trials, and their convictions on fabricated and politically motivated charges."