The studio of Russian director Aleksei Uchitel, who has been under pressure from conservative activists for his film highlighting the romantic youth of Tsar Nicholas II, has reportedly been attacked.
Russian media reports quoted police in St. Petersburg as saying on August 31 that unknown assailants threw Molotov cocktails into the building that houses Uchitel's studio at 3:30 a.m.
According to the reports, the fire was extinguished before police arrived and nobody was hurt.
The reports have not been officially confirmed by city authorities.
Uchitel said earlier that he had received verbal threats from representatives of a group that calls itself Christian State-Holy Rus, which along with other Orthodox activists and conservatives called unsuccessfully for a ban on his film Matilda.
On August 10, Russia's Culture Ministry said it had issued a screening certificate for the film, which depicts Nicholas II's relationship with teenage ballet dancer Matilda Kshesinskaya.
The ministry said the film had been cleared for release nationwide on October 26.
Some Russian Orthodox figures and hard-line nationalists vehemently opposed allowing the film to be shown, claiming it besmirches the memory of Nicholas, who was canonized by the Russian Orthodox Church in 2000.
The campaign to ban the film was led by Natalya Poklonskaya, a controversial member of parliament who has expressed monarchist views and served as the chief regional prosecutor in Crimea following its armed takeover by Russia in March 2014.
Ramzan Kadyrov, the Kremlin-backed head of Chechnya, argued that Matilda should be barred from theaters in the mostly Muslim regions in Russia's North Caucasus, saying it was a "premeditated insult to the feelings" of religious believers.
The film tells the story of a romance between Nicholas and Kshesinskaya when he was an unmarried crown prince. Trailers showing romantic scenes between the young prince and Kshesinskaya have outraged conservative critics.
The affair ended in 1894, when Nicholas married the German princess who became Empress Aleksandra. Kshesinskaya later married the tsar's cousin, Grand Duke Aleksandr Vladimirovich. She died in 1971.
Conservatives deny the well-documented affair took place, with some claiming that it would have been impossible for a prince to fall in love with a Pole who was "utterly homely.”
Uchitel has received support from several prominent Russian filmmakers.
The tsar and his family were killed by a Bolshevik firing squad in July 1918.