A Russian court has sentenced the Ukrainian film director Oleg Sentsov to 20 years in prison after a trial described by Amnesty International as “redolent of Stalinist-era show trials”.

Sentsov, 39, and his co-defendant Alexander Kolchenko, who received a 10-year sentence at the trial on Tuesday, were accused of planning terrorist acts in Crimea after the peninsula was annexed by Russia last year.

The trial was littered with irregularities: Sentsov said he had been tortured, while investigators dismissed the bruises on his body as being the result of a supposed penchant for sadomasochistic sex. The main prosecution witness recanted in the courtroom and said his evidence had been extorted under torture. He said no “acts of terrorism” were ever committed except for an arson incident in which nobody was injured and Sentsov denied involvement.

Ukrainian film-maker tells Russian court he will 'suffer or die' for his beliefs Read more

Nevertheless, prosecutors asked for him to be given a 23-year sentence and Kolchenko a 12-year term. On Tuesday, the panel of three judges in a Rostov military court handed down their verdict. When the judges asked the pair if they understood the verdict, they smiled and sang the national anthem of Ukraine.

In an impassioned message to the court last week, Sentsov said he had not been prepared to accept deals with the investigators, who tortured him and pressed him to confess. He said: “When they put a bag on your head, beat you up a bit, half an hour later you’re ready to go back on all your beliefs, implicate yourself in whatever they ask, implicate others, just to stop them beating you. I don’t know what your beliefs can possibly be worth if you are not ready to suffer or die for them.

“I am not going to beg for leniency. Everything is already clear. A court of occupiers cannot be just by definition.”

Sentsov directed the 2011 feature film Gamer, but stopped work on a new movie when Russia began to intervene in Crimea. He coordinated relief efforts for the Ukrainian soldiers who were blockaded inside their bases by Russian troops.

Heather McGill, a researcher at Amnesty International, said: “This whole trial was designed to send a message. It played into Russia’s propaganda war against Ukraine and was redolent of Stalinist-era show trials of dissidents. This trial was fatally flawed and credible allegations of torture and other ill-treatment have been ignored by the court.”

International film directors, including Ken Loach, Mike Leigh and Wim Wenders, have signed an open letter to the Russian president, Vladimir Putin, calling for Sentsov’s release and an investigation into claims of torture against him. Russian directors have also joined the appeals.

Andrei Zvyagintsev, whose most recent film, Leviathan, won a Golden Globe, said on Monday that he had read the documents from the court case and found them unconvincing. He asked the Russian authorities to “either release [Sentsov] or try him only for what you can prove irrefutably”.

Alexander Sokurov, the director of Russian Ark and other acclaimed films, described the case as rather fantastic. In a blog post, he wrote that Sentsov’s actions were “nothing more extremist than civil protest”.

Ken Loach, Mike Leigh and others call for release of Ukrainian director Read more

The UK minister for Europe, David Lidington, said he was deeply concerned about the verdict and described the charges as disproportionate and politically motivated.

Lawyers for Sentsov and Kolchenko said they always expected the court to issue a guilty verdict: innocent verdicts are almost unheard of in the Russian legal system. Their main hope is for some kind of prisoner exchange with Ukraine, possibly for Russian soldiers captured in the east of the country.

In Ukraine, the case has prompted a wave of criticism, and Sentsov’s Ukrainian lawyer is preparing a criminal case against the prosecutors, investigators and others involved in the trial, for the illegal kidnapping and torture of a Ukrainian citizen. The court ruled that Kolchenko and Sentsov automatically became Russian citizens after the annexation of Crimea, and tried them as such.

The Ukrainian MP Mustafa Nayyem wrote on Facebook that he believed Russian citizens should be admitted to Ukraine in future only after answering a question about whether they believed the sentence in the Sentsov case to be just.

The case has been seen as an attempt to discourage further dissent in Crimea, which was annexed after a speedily held referendum last spring. The majority of residents supported joining Russia, but Russia has done everything to prevent the disgruntled minority from protesting. Many ethnic Ukrainians and Crimean Tatars have left for mainland Ukraine. A small group of people who gathered to celebrate the birthday of the Ukrainian poet Taras Shevchenko in March were arrested for holding Ukrainian flags.

Putin spent three days in Crimea last week, descending to the depths of the Black Sea in a bathyscaphe to inspect the wreck of a Byzantine trading ship and directing government officials to boost tourism in the region.

'A court of occupiers cannot be just': Ukrainian director's courtroom speech Read more

Ukraine claims Russia is holding at least 10 of its citizens on various charges ranging from espionage to murder. The best known is the military pilot Nadezhda Savchenko, who is accused of being an artillery spotter for the Ukrainian forces and involved in the deaths of two Russian journalists. Her lawyers say she was abducted and brought across the border to Russia. She is due to go on trial in the southern Russian town of Donetsk, close to the Ukrainian border, in the coming weeks.