MOSCOW (AP) — A Ukrainian filmmaker who has been in jail for more than a year on Tuesday pleaded not guilty to charges of conspiracy to commit terrorism.

Critics have dismissed Oleg Sentsov's prosecution as revenge for his pro-Ukrainian position in Russia-occupied Crimea. Sentsov, a Crimean native, was a vocal voice against Russia's annexation of Crimea which followed a hastily called referendum in March.

The 39-year-old Sentsov was arrested in Crimea's capital in May 2014 after a pro-Ukrainian rally protesting the annexation.

At the opening of his trial in the southern city of Rostov-on Don on Tuesday, Sentsov pleaded not guilty and insisted the case against him is a fabrication, Russian news agencies reported.

Sentsov's defense team describes Sentsov's arrest in May 2014 as a kidnapping.

Sentsov, who unlike many Crimeans didn't apply for Russian citizenship, was grabbed on the street in Crimea's capital, Simferopol, by Russian security agency FSB and resurfaced days later in custody in Moscow.

Sentsov insists that he should be tried by a Ukrainian court since he didn't apply for Russian citizenship, although the court treats him as a Russian citizen after he was given a passport in custody.

Russian officials say Sentsov's arrest was legal.

Also on trial with Sentsov is anti-fascist activist Alexander Kolchenko. Both men are suspected of collaborating with the Ukrainian right-wing organization Right Sector to perpetrate acts of terrorism.

The Crimean native faces up to 20 years behind bars if found guilty.

Ukraine says Sentsov is a political prisoner and should be immediately released.