An Ulyanovsk court on Wednesday convicted Left Front leader Sergei Udaltsov on a charge of assaulting a pro-Kremlin youth activist and ordered him to carry out 240 hours of community service.
The charge relates to an April incident in which Udaltsov is alleged to have struck Young Guard activist Anna Pozdnyakova during a local Communist Party rally.
According to Pozdnyakova, she suffered a concussion and blood loss after being hit. Video footage later posted on YouTube showed her looking unharmed and boasting to friends that Udaltsov had struck her.
Udaltsov denied his guilt throughout the court proceedings. Judges refused to review the video footage in which Pozdnyakova boasts of being hit, RIA-Novosti reported.
Local authorities will determine the place and type of work that Udaltsov must complete, according to Lenta.ru. Rules state that a maximum of four hours of community service can be carried out per day, meaning that Udaltsov could have to spend at least two months in the Urals city.
Observers said they thought Wednesday's sentence was linked to Udaltov's status as a protest leader.
"I know Sergei Udaltsov well and will never believe that he hit a woman," Lev Ponomaryov, a veteran human rights defender and head of the For Human Rights movement, told Interfax.
"The decision of the court is absolutely politically motivated," he said.
Ulyanovsk prosecutors opened the criminal case on assault charges against Udaltsov at the beginning of May, just a few days before an opposition protest Udaltsov co-organized.