At least one policeman has been injured and several protesters have been detained after scuffles outside the Ukrainian parliament in Kyiv, the capital.
Several hundred people were rallying on Tuesday outside the Supreme Rada to protest a new law governing the areas in the country's east under separatist control. The conflict between the Russian-backed separatists and Ukrainian government troops has been raging since 2014, killing more than 10,000 people.
Ukrainian police say the protesters outside the Rada used pepper spray and pelted police with stones and tires.
The protesters were led by Semyon Semyonchenko, former commander of a volunteer battalion in eastern Ukraine suspected of human rights violations.
Semyonchenko and his supporters criticize the new law as being too lenient on separatist leaders.