A Russian man is facing charges over a lecture he gave about the philosophy of yoga, a popular practice in the country of which even Prime Minister Dmitry Medvedev is a keen adherent.

Dmitry Ugai , 44, will appear at a court hearing in St Petersburg on 18 January for his talk on 22 October 2016 at a Vedic festival in Russia's second city, where he discussed yoga and its spiritual texts and teachings.

Less than three-quarters of an hour into the talk, police arrested him. Critics say he has fallen victim to a new Big-Brother like anti-terror law which forbids missionary activities in unapproved spaces.

He told the Russian channel Rain TV: "The policeman asked if I understood that I was engaging in illegal missionary work and what awaits me as a result".

He refused to admit guilt in a document he was asked to sign and was released.

A document submitted to court, subsequently dismissed by a judge, accused him of illegal missionary work. Another document accused him of pushing information about the Hindu tradition of Vaishnavism to boost its community membership.

"I never mentioned the name of that association or the word Vaishnavism. The entire contents of my lectures can be found in books on Indian philosophy, which is taught at universities," he said.

Yoga is popular in Russia. When Dmitry Medvedev became prime minister in 2007 he said "little by little, I am mastering yoga". A group of his supporters called Medvedev's Girls performed yoga exercises on Red Square in 2015 to promote the practice.

Critics say Ugai is falling foul of repressive legislation making it illegal to speak publicly about religion unless registered with the authorities.

Dubbed 'Yarovaya law', after its main sponsor in Russian parliament, it was passed it in 2016 to oppose Islamist activity in Russia's North Caucasus.

But Alexander Verkhovsky, from the Moscow-based Sova Centre, which monitors anti-extremism measures, said the legislation's wording was too opaque.

"It's entirely unsurprising that police officers on the ground cannot work it out. Because the law exists, it is going to be implemented somehow. It cannot be implemented well because of the stupidity of the phrasing," he told Radio Free Europe.

In August 2016, a follower of the Hare Krishna movement was arrested after talking on the street to two people about his faith. Also, Salvation Army employees in Vladivostok were ordered by police to burn Bibles they said were not labelled properly, the Moscow Times reported.

On his blog, Ugai wrote: "I am worried about the randomness of this law, which can mean that my fellow citizens who practice yoga and study Indian philosophy can be persecuted. There are signs that there's a campaign unfolding against an entire culture ."