Ukrainian security forces, demonstrators clash

A riot policeman takes a rest from the fighting in central Kiev.   (Sergei L. Loiko / Los Angeles Times)

Riot police regroup for an attack on protesters’ barricades in Kiev’s Independence Square.   (Sergei L. Loiko / Los Angeles Times)

Protesters take shelter behind wooden shields as police use grenades and bullets in Kiev’s Independence Square on Wednesday.   (Sergei L. Loiko / Los Angeles Times)

Exhausted riot police sleep on the sidewalk in central Kiev after clashes with the protesters in Independence Square.   (Sergei L. Loiko / Los Angeles Times)

Protesters remove material from Independence Square to hurl at police.   (Sergei L. Loiko / Los Angeles Times)

Flames rise behind a monument to Kiev’s founders as antigovernment protesters clash with riot police in Kiev’s Independence Square. As many as 19 people were killed in the violence, including both protesters and police. Hundreds of people were injured.   (Efrem Lukatsky / Associated Press)

Antigovernment demonstrators clash with police at Independence Square in Kiev, Ukraine, as flames engulf the main protest camp there.   (Genya Savilov / AFP / Getty Images)

An antigovernment protester catches on fire during clashes with riot police outside Ukraine’s parliament in Kiev.   (Efrem Lukatsky / Associated Press)

Protesters are left bloodied by the clash with police in Kiev, Ukraine.   (Olesksandr Ratushniak / AFP/Getty Images)

Police shield themselves during clashes with protesters in Kiev, Ukraine.   (Genya Savilov / AFP / Getty Images)

Antigovernment protesters clash with police in front of the Ukrainian parliament building in Kiev.   (Sergei Supinsky / AFP / Getty Images)

Protesters throw stones at police, who fired rubber bullets in the Kiev clashes.   (Anatoli Stepanov / AFP / Getty Images)