MOSCOW) - Ukrainian military command centers in the cities of Kyiv and Kharkiv have been attacked by missile strikes, the Ukrainska Pravda news website cited a Ukrainian interior ministry official as saying on Thursday.
Russian President Vladimir Putin authorized a military operation in eastern Ukraine on Thursday in what could be the start of war in Europe over Russia's demands for an end to NATO's eastward expansion.
Shortly after Putin spoke, a Reuters witness heard the sound of what appeared to be explosions in the distance from the capital, Kyiv. Gunfire rattled near the capital's main airport, the Interfax news agency said.
Explosions also rocked the breakaway eastern Ukrainian city of Donetsk and civilian aircraft were warned away as the United States said a major attack by Russia on its neighbor was imminent.
Putin said he had authorized a special military operation in breakaway areas of eastern Ukraine and clashes between Russian and Ukrainian forces were only a matter of time.
Hours earlier, pro-Russian separatists issued a plea to Moscow for help to stop alleged Ukrainian aggression - claims the United States dismissed as Russian propaganda.
Putin said he had ordered Russian forces to protect the people and demanded Ukrainian forces lay down their arms.
"All responsibility for bloodshed will be on the conscience of the ruling regime in Ukraine," Putin said.
He repeated his position that NATO expansion to include Ukraine was unacceptable and said Russia had been left with no choice but to defend itself against what he said were threats emanating from Ukraine.
The scope of the Russian military operation was not immediately clear. Moscow has long denied that it has plans to invade despite massing tens of thousands of troops near its neighbour.
Ukrainian President Volodymyr Zelenskiy said on Wednesday that Moscow had approved an offensive and had not replied to an invitation for talks.
"Today I initiated a telephone conversation with the President of the Russian Federation. The result was silence," he said.
U.S. President Joe Biden said his prayers were with the people of Ukraine "as they suffer an unprovoked and unjustified attack by Russian military forces".
"President Putin has chosen a premeditated war that will bring a catastrophic loss of life and human suffering. Russia alone is responsible for the death and destruction this attack will bring, and the United States and its Allies and partners will respond in a united and decisive way. The world will hold Russia accountable."
He said he would announce further sanctions on Russia on Thursday, in addition to financial measures imposed this week.
The Russian operations began as the U.N. Security Council held an emergency meeting on the Ukraine crisis in New York.
A draft resolution calling out Moscow over its actions toward its neighbor is doomed to fail due to Russia veto power, however a Security Council diplomat said it would put Russia on notice that it is "not in compliance with international law."
(Reporting by Olzhas Auyezov; Editing by Kim Coghill)