A Russian court on Tuesday sentenced a law student writing a thesis on countering radicalism to two and a half years in prison for reposting "extremist" images online.

Alexander Kruze, 23, was found guilty of "calling for extremist acts" and "inciting racial hatred on the internet" in late December for reposting four nationalist images on Russian social media platform Vkontakte in July 2016.

He said the posts were intended to poll the public as part of his studies, but a court ruled that they had an extremist character.

The student had been working on his dissertation on different types of radicalisation in Russia for months, his lawyer Andrei Milevski told AFP.

The first image called for taking action against communists, the second contained anti-Semitism, the third condemned illegal immigration and the fourth called on regime change in Russia.

"I have been collecting material for over four years and as part of my investigation I re-publish texts and images on purpose to provoke a discussion in which I participate myself," Kruze told AFP on Tuesday.

"Depending on the subject of the (social media) post, I pretend to be a Russophobe, a racist or a Ukrainian nationalist or separatist," said Kruze, who lives in Stary Oskol, a city 160 kilometres (100 miles) from the Ukrainian border.

"It was especially unpleasant to talk with anti-Semites because I have some Jewish blood in me," he added.

Kruze's classmate Denis Mirchev told AFP that the law student often spoke about "organising experiments to prepare for his thesis".

"When I was at his house, I saw the documents he was collecting to study how people view illegal immigration in Eastern Europe and in Russia," Mirchev told AFP.

Despite the decision to send him to prison, Kruze said he wants to join Russia's FSB security service to "fight extremism".

Meanwhile, Kruze will have to spend two and a half years in a detention centre for offenders who have committed minor crimes.

Kruze is one of a growing number of Russians jailed for social media posts on extremism charges.

In 2017, 43 people in Russia were sentenced to prison terms for internet posts, according to a human rights report published last week.