Russians are holding a citizen of Ukraine, Crimean Dmytro Papenko, in occupied Simferopol, the Zmina media outlet has reported, citing its own source.
"47-year-old Dmytro Papenko helped our country. He has no family and no-one to turn to for help. Ukrainians should know about him," the source said.
Papenko was detained by the Russians in Sevastopol on 1 December 2022.
They accused him of espionage and opened criminal proceedings under Article 275 of the Russian Criminal Code.
Papenko is being held in Simferopol detention centre No 2.