Ukraine says Russia is refusing to hand over jailed Ukrainian filmmaker Oleh Sentsov.
Ukrainian Deputy Justice Minister Serhiy Petukhov posted a copy of the refusal letter on Facebook on October 21, in which Russia's Justice Ministry says it is "impossible" to transfer Sentsov to Kyiv because he holds Russian citizenship.
Sentsov became a Russian citizen in March 2014, when a Russian law conferred citizenship on all residents of the Crimean Peninsula, according to the letter.
Crimea's Russia-backed authorities convicted Sentsov in 2015 of conspiring to commit terrorism on the annexed Ukrainian peninsula, and sentenced him to 20 years in prison.
Sentsov, a native of Crimea, was a vocal opponent to Russia's annexation of the peninsula in March 2014.
Amnesty International described his trial as "fatally flawed."