US President Joe Biden has responded to what he calls an "unprovoked and unjustified attack by Russian military forces".
According to BBC he says "the prayers of the entire world are with the people of Ukraine".
"President Putin has chosen a premeditated war that will bring a catastrophic loss of life and human suffering," he says.
"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."
Biden says he will address Americans on Thursday about the consequences Russia will face.
He says he will be monitoring the situation from the White House and will meet with G7 leaders in the morning before announcing "further consequences" for Russia.
Biden says there will be a "strong, united response" from Nato allies that deters any aggression against its members.
"Tonight, Jill and I are praying for the brave and proud people of Ukraine," he says.
