The crisis in Ukraine has entered a dangerous new phase, as pro-Russian demonstrators and Ukrainian security forces clashed on Sunday in the eastern city of Slaviansk.
Ukrainian forces launched what they called an "anti-terrorist" operation to clear pro-Russian separatists from the police headquarters that protesters had seized the day before.
One Ukrainian state security officer was killed, and at least five other government officials were injured.
Reports say there were also casualties on the pro-Russian side.
An "act of aggression by Russia" is what Ukraine calls the recent raids by pro-Russian activists in eastern Ukraine.
"We want to unite with Russia. We will be thankful to Russia, if they help us. But we'll stay until victory. Honestly, I am not afraid to die for freedom."
Kiev has mobilized its troops to take action as Russian forces took control of more areas in the eastern part of the country, including in the city of Kramatorsk on Saturday and Slaviansk.
During a phone call between U.S. Secretary of State John Kerry and Russia's Foreign Minister Sergei Lavrov on Saturday, Kerry expressed his concerns about armed attacks in eastern Ukraine, and warned of additional consequences if the situation does not de-escalate.
On Sunday, Lavrov told Ukrainian authorities that any military action by Ukraine could undermine upcoming talks on the crisis.
Ukraine, Russia, the U.S. and the EU are scheduled to enter talks on the crisis in Geneva on Thursday.
In related news, the White House announced that Vice President Joe Biden will make a trip to Kiev on April 22nd to show U.S. support for Ukraine's new government.
He will be the most senior U.S. official to travel to the country since the crisis erupted.
Kwon Soa, Arirang News.