One national guard member has been killed and over 100 injured in violent protests outside Ukraine's parliament, the interior ministrysaid.
Clashes between nationalists and riot police erupted after MPs gave initial backing to reforms for more autonomy in the rebel-held east.
Some in the crowd lobbed what police said were live grenades at officers protecting parliament.
The reforms are part of a peace plan to end fighting in eastern Ukraine.
The Ukrainian President, Petro Poroshenko, said the violence was "a stab in the back".
Protesters led by the populist Radical Party and the ultra-nationalist Svoboda (Freedom) party - who oppose any concession to the Russian-backed separatists - gathered outside parliament early on Monday.
After a rowdy debate, 265 MPs out of 450 backed the first reading of the decentralisation bill, granting more powers to areas of Donetsk and Luhansk.
Initially, there were only minor clashes but a BBC correspondent then heard small explosions followed by a much larger one - apparently from a grenade.