MOSCOW (AP) — Ukraine says Russia is refusing to hand over jailed Ukrainian filmmaker Oleg Sentsov, who was convicted of conspiracy to commit terror attacks by a Russian military court in 2015 and sentenced to 20 years in prison.

Ukraine's Deputy Justice Minister Sergiy Petukhov posted a copy of the refusal letter on Facebook on Friday in which Russia's Justice Ministry said it was "impossible" to transfer Sentsov to Ukraine because he holds Russian citizenship.

The Russian Justice Ministry said Sentsov was made a Russian citizen in March 2014 when a new Russian law conferred citizenship on all residents of Crimea, according to the letter.

Sentsov, a native of Crimea, was a vocal opponent to Russia's annexation of the peninsula. Critics say his prosecution was punishment for his pro-Ukrainian position.