People attend a rally organized by supporters of EU integration in central Kiev.
Police report that people wearing masks pulled down the statue of the Russian revolutionary leader Lenin in the centre of the Ukrainian capital city.
Hundreds of thousands of people have taken to the streets in the Ukrainian capital Kiev seeking the resignation of the government for refusing a deal on closer ties with the European Union.
Protest leaders have given President Viktor Yanukovych 48 hours to dismiss the government and have set up barricades outside the Yanukovych's offices.
"This is a decisive moment when all Ukrainians have gathered here because they do not want to live in a country where corruption rules and where there is no justice," said world heavyweight boxing champion-turned-politician Vitaly Klitschko.
Yanukovych has said he shelved the EU deal after Russian opposition, although Vladimir Putin has asked Kiev to join a Russian-led customs union.
The Ukrainian Security Service said it was investigating some politicians on suspicion of what it called "actions aimed at seizing state power".
Both Russia and Ukraine denied that the issue of Ukraine joining the customs union along with Belarus and Kazakhstan came up during the Putin-Yanukovych meeting in Sochi, in southern Russia, on Saturday.
Correspondents had earlier speculated that an agreement on Ukraine joining the customs union might be reached in return for reduced energy prices.
The two neighbours have also been trying to resolve a long-running dispute over energy supplies.