Joe Biden: President Putin has chosen a premeditated war that will bring a catastrophic loss of life and human suffering

US President Joe Biden said Washington and its allies would respond in a united and decisive way to "an unprovoked and unjustified attack by Russian military forces" on Ukraine.

Biden will address Americans on Thursday about the consequences he says Russia will face.

"President Putin has chosen a premeditated war that will bring a catastrophic loss of life and human suffering," Mr Biden said. "The world will hold Russia accountable."

Russian President Vladimir Putin announced a "military operation" in Ukraine's Donbas region.

Russia is launching its military operation just days after recognising the self-proclaimed people's republics of Donetsk and Luhansk in eastern Ukraine.