Ukrainian far-right extremists clashed with anti-riot police outside the parliament in Kiev, as lawmakers voted against a bill to officially recognise a controversial World War II partisan group as nationalist heroes.
The violence followed a large demonstration held by the nationalist Svoboda party to commemorate the Ukrainian Insurgent Army's (UPA) effort against Soviet occupation.
Both groups however denied their members were involved in the violence.
The rioters, many with their face covered, hurled smoke grenades and stones at security forces who responded using batons to disperse the mob, amid unconfirmed reports that shots had been fired.
The Interior Ministry said 50 people were arrested.
The UPA is at the roots of Ukraine ultra-nationalism, as the WWII guerrilla group fought against Soviet occupation, at times striking a loose alliance with the Nazis.
Besides turning down the proposal to honour UPA's role in the history of Ukraine, the parliament also voted a law creating an anti-corruption bureau and other measures to fight graft.
Lawmakers also approved a new defence minister — former National Guard head Stepan Poltorak — who will have to face the security crisis in the restive east of the country.