Anti-government protesters in Ukraine on Tuesday set on fire the headquarters of the ruling Party of Regions in downtown Kiev in a fresh wave of violence. Earlier in the day, protesters calling for constitutional changes to limit presidential powers torched two vehicles outside the parliament building and attacked riot police with Molotov cocktails. The police used stun grenades and tear gas to break down the crowd. According to the Interior Ministry, at least 10 police officers were injured, while local media said dozens of protesters were hurt. Inside parliament, opposition politicians blocked the speaker's tribune, urging the deputies to discuss their call for constitutional reform that would curb the powers of President Viktor Yanukovych. They also demanded early presidential and parliamentary elections to end the unrest now in its third month. Massive rallies erupted last November in Kiev following the government's decision to backtrack an association agreement with the European Union. The rallies snowballed into a nationwide movement demanding the impeachment of Yanukovych, the resignation of the government and the dissolution of the parliament. Unrest in central Kiev has left at least four people dead and hundreds of others injured.