Protesters clashed with riot police in the Ukrainian capital on Sunday after tough anti-protest legislation, which the political opposition says paves the way for a police state, was rushed through parliament last week.
A group of young masked demonstrators attacked a cordon of police with sticks and tried to overturn a bus blocking their way to the parliament building after opposition politicians called on people to disregard the new legislation.
The interior ministry said 30 police were hurt, including more than 10 admitted to hospital and four in serious condition.
Despite appeals from opposition leaders not to resort to violence, and a personal intervention from boxer-turned-politician Vitaly Klitschko, protesters continued to throw smoke bombs and hurl fireworks and other objects at police.
Ukraine has experienced difficult days before but few have been so complex or so pivotal.
The Ukrainian government says it is is ready to use all tools available to restore order if violence and unrest continues.
These are difficult days for Ukraine, a country edging toward its second revolution in a decade.