Hundreds of protesters clash with riot police in the centre of the Ukrainian capital, following the passage of harsh anti-protest legislation last week seen as part of attempts to quash anti-government demonstrations.
Some were injured and medics were seen treating them.
Opposition leader Vitali Klitschko tried to stop the protesters from attacking police, but he came under attack.
The clashes occurred shortly after a large peaceful rally on Kiev's main square, part of the anti-government protests rocking Ukraine since President Viktor Yanukovych's decision to freeze ties with the European union and embrace Russia instead.
Since then, Moscow has promised a 15 billion US dollar (£9 billion) bailout loan to aid Ukraine's struggling economy.
Scores of opposition leaders and journalists have been attacked, harassed and prosecuted, since the protests started on November 21.
Last week, Yanukovych caused uproar at home and abroad when he approved a number of laws that limit Ukrainians' rights to protest, civic activism and free speech.
The laws prohibit demonstrators from wearing masks or hard hats at rallies, prompting many to don theatrical masks and kitchen pots at Sunday's rally.