Religious conservatives in Russia, increasingly influential under President Vladimir Putin, are campaigning to block the release of a 'blasphemous' film depicting an affair between a young ballerina and the last tsar, considered a martyr by the Orthodox church.

The director Alexei Uchitel's 'Matilda', to be released internationally in late October, tells the tale of the late-19th century romance between Nicholas II, before he became tsar, and half-Polish dancer Matilda Kshesinskaya, who described the relationship in her memoirs.

Nicholas 'loved me dearly', she wrote. 'I adored Nikki, I thought only of him, of my sweetheart.'

Cinema operators planning to show 'Matilda' are coming under pressure, Uchitel told Reuters in an interview, ranging from behind-the-scenes lobbying to arson threats.

The opposition has ranged from street demonstrations to appeals from prominent clergy, with some activists making physical threats against cinemas who plan to show it.

Uchitel said: 'The tense atmosphere for the studio these past few months, for those who are making the movie and for the exhibitors, is a serious test. They could say [to a cinema] over the phone: You have two showings, for the sake of form, and that's it. I'm not afraid of an official ban in particular regions, but I fear this kind of pressure.'

The director said that the main Russian distributor of the film, Karo, had received a letter from a hardline Orthodox Christian group, calling itself 'Christian State - Holy Rus'.

Karo and 'Holy Rus' representatives did not comment to Reuters.

But in a statement on its website site, the hardline group said the film was an insult to Russia and its history and warned that it could drive some people to commit violence, such as setting cinemas on fire. It denied it planned to do anything illegal or had anything to do with acts already committed.

Last week, someone tried to set fire to a studio complex in St Petersburg that houses Uchitel's studio. There was minor damage to a part of the complex used by another organisation.

And in the early hours of Monday morning, a man drove a car packed with gas canisters into the entrance of a cinema in Yekaterinburg, the city where Bolshevik revolutionaries executed the Tsar and his family.

Authorities said the driver had been arrested. The cinema, which caught fire, had been hosting a film festival at which the chairman of the festival jury spoke in support of Uchitel.

Prominent Russian arts figures say there is a broader trend of artistic freedom being restricted by cultural conservatives who have grown in influence under Putin.

But Deputy Culture Minister, Vladimir Aristarkhov, has praised the film and called the campaign against it slanderous. Uchitel said he had had nothing but support from the ministry.

For many religious believers, the story told in 'Matilda' is the slander.

Bishop Tikhon Shevkunov, the head of the Orthodox Church's Patriarchal Council on Culture, said in response to Reuters' questions that the film contained 'lies about our history, lies about the circumstances of the life of the royal family'. He added: 'From an artistic point of view it is simply unbelievably crass.'

But he said the church was not seeking to ban the film and all protests against it should be within the law.

Natalia Poklonskaya, a pro-Kremlin member of the lower house of Russia's parliament, said the film was an insult to religious believers. She said she had filed a request to the Prosecutor-General's office asking it to protect them from the movie.

Three Muslim-dominated regions of southern Russia - Chechnya, Dagestan and Ingushetia - have said they will not allow cinemas to show 'Matilda'.

Jambulat Umarov, a minister in Chechnya, said that a movie should accurately portray historical events and 'not lead the viewer into the boudoir'. He added: 'Why stir up hatred on the other side? Why stir up rage?'

The tsar and his family were executed soon after the 1917 Bolshevik Revolution - an event whose hundredth anniversary is being commemorated this year.

A company called Centrefilm, which owns four cinemas in Moscow, said it would not show the film, branding it as 'blasphemous and insulting'.

Two big cinema companies, Luxor and Cinemapark, said they would screen it. 'We tell police about any threats we get,' said a spokesperson for Cinemapark.

The row over the movie comes against the backdrop of growing links between the Russian Orthodox Church and Putin, amid a crackdown on other religious minorities.

In April for the first time, Russia was officially included among the worst countries in the world for religious freedom because of its ongoing crackdown against religious minorities, foreign missionaries and evangelists and a ban that month on Jehovah's Witnesses.

The US Commission on International Religious Freedom (USCIRF), which monitors religious freedom violators for the State Department, listed Russia among six new top-tier 'countries of particular concern' in its latest annual report.

The former Soviet state is the only country where repression of religious freedom has intensified and expanded since USCIRF began monitoring it, according to officials.

Yet at the same time, Russia's Orthodox Church is consolidating its power and pursuing close ties with Putin.

The new closeness between Church and state comes some 26 years after the end of the Soviet-era repression of the Russian Orthodox Church, which has around 165 million members worldwide.

President Putin and Patriarch Kirill, the head of the Russian Orthodox Church, share similarly authoritarian positions on human rights as well as issues relating to foreign policy, family values and more.

Last year, Putin drew international protests after introducing legislation which imposes harsh restrictions on religious groups. Known as the 'Yarovaya Law,' the measure included new police and counterterrorism measures that critics said directly echo the sweeping powers wielded by the KGB.

Within the law were tight restrictions on religious groups, especially smaller denominations.

Since the breakup of the Soviet Union, Russia's dominant denomination, the Orthodox Church, has flourished.

Earlier this year, the Orthodox Church was steeped in controversy over its bid to take control of St Petersburg's landmark church, St Isaac's Cathedral, which was a museum. The row appeared to be a symbolic demonstration of the Church's increasing dominance.

Additional reporting by Reuters.