The world will hold Russia accountable for the death and destruction due to the "unprovoked" and "unjustified" attack on Ukraine and the US and its allies will respond in a "united and decisive" way, President Joe Biden has warned, as his Russian counterpart Vladimir Putin on Thursday announced a special military operation in eastern Ukraine.

President Putin, in a televised address, announced a military operation in Ukraine, claiming it is intended to protect civilians.

Reacting to Putin's move, Biden said his Russian counterpart 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.

In a late Wednesday night statement, Biden said the prayers of the entire world are with the people of Ukraine as they suffer an "unprovoked" and "unjustified" attack by Russian military forces.

The president said he will be monitoring the situation in Ukraine from the White House and will continue to get regular updates from his national security team.

Tomorrow, I will meet with my G7 counterparts in the morning and then speak to the American people to announce the further consequences the United States and our Allies and partners will impose on Russia for this needless act of aggression against Ukraine and global peace and security, he said.

We will also coordinate with our NATO Allies to ensure a strong, united response that deters any aggression against the Alliance. Tonight, Jill and I are praying for the brave and proud people of Ukraine, Biden said.

Putin said Russia's move came in response to threats emanating from Ukraine. He also warned other countries that if they attempted to interfere with the Russian military operation they would see consequences they have never seen .