A huge rally has been taking place in the Ukrainian capital to oppose a government decision not to sign a deal on closer EU ties, despite a ban.
Casualties were reported after clashes between protesters and police on the fringes of the rally.
Police used tear gas and stun grenades to push back protesters near the presidential office.
Elsewhere in the city centre, protesters stormed the city council building and took it over.
About 100,000 people rallied on Independence Square, Kiev, defying a ban imposed a day earlier. Protesters are demanding the resignation of the government and new elections.
President Viktor Yanu-kovych says Russian pressure was behind his decision not to sign the deal.
Demonstrators tried to approach President Yanukovych’s headquarters, commandeering a bulldozer to break through police lines.
Police used tear gas and stun grenades to force back the crowd, who responded by throwing bricks. Witnesses said dozens of people with head injuries were taken away by ambulances.
A police spokeswoman said that about 100 police were injured in the clashes there.
The mainstream opposition and its leaders said they had nothing to do with those engaged in violence.