
Right-wing activists blocked the entrance to Russia's embassy to prevent Russian citizens from voting.
One demonstrator has been detained in a scuffle with police.
A leader of the nationalist Svoboda party, Igor Miroshnichenko was among the demonstrators Sunday. He said Ukraine should "not allow the enemy and state aggressor that stole Crimea to conduct illegal elections in Ukraine."
Russia annexed Crimea in 2014 following the months of unrest that drove out Ukraine's Russia-friendly president.