Supporters of Russian anti-war politician Boris Nadezhdin were arrested for posting "extremist" content in their personal chats on Telegram, local media reported.

Nadezhdin is a Russian opposition politician who intended to compete against the current president, Vladimir Putin, in the upcoming presidential election but was barred from entering the race after Russia’s electoral committee declared a high proportion of signatures supporting his nomination invalid.

After he was disqualified from the race, Nadezhdin called on his supporters to volunteer as election observers to ensure the fair counting of votes.

Igor Krasnov, one of the volunteers and the head of Nadezhdin’s campaign headquarters in the city of Vladivostok, was arrested earlier this week after allegedly using a rainbow flag emoji in a group chat with 11 members in December. He will be held in custody for six days.

Russian media reported, citing sources in Nadezhdin’s team, that one of the chat’s participants had their Telegram account hacked, giving Russian law enforcement access to the messages.

In Russia, LGBTQ activists are labeled as "extremists" and can face arrest and prosecution. Individuals who display rainbow-colored items may receive jail time or fines.

Two other campaign volunteers, who were part of the same Telegram chat as Krasnov, were arrested in their university dorm overnight. They will be held in custody for six days and are required to pay a $300 fine for sharing online a political meme and a sticker featuring an extremist symbol.

Another volunteer was arrested during his university lecture for sharing information with prohibited symbols. Nadezhdin's team explained that the “prohibited” content in question was his digital avatar featuring an anime character. He will be held in custody for five days.

On Thursday, Nadezhdin’s team published photos of documents confirming the aforementioned arrests on its Telegram channel.

These arrests took place in the lead up to the Russian presidential election, which is scheduled to take place from March 15 to 17. It will be Russia's first-ever three-day-long presidential election and the first instance when residents from certain regions, including Moscow, can cast their votes online.

Russian law enforcement has previously arrested citizens for publishing "prohibited" content online. However, in most cases, this content was shared publicly rather than in personal chats.

In January, a 72-year-old Russian woman received a more than 5-year prison sentence for sharing anti-war messages on social media platform VKontakte. In March of last year, a Moscow court sentenced 63-year-old railway worker Mikhail Simonov to seven years in prison for sharing alleged disinformation about the army and anti-war posts on VKontakte.