US President Joe Biden has announced additional sanctions against Russia and the deployment of more troops to Europe as conflicts in Ukraine continue to evolve.

Speaking from the East Room of the White House, Biden on Thursday said the new measures will target major Russian banks, limit the country's "ability to do business in dollars, euros, pounds, and yen," and curtail Moscow's high-tech imports and its ability to upgrade the military.

The US President said he had authorised "deployment of ground and air forces stationed in Europe to the eastern flank," as well as "additional US force capabilities to deploy to Germany" as part of the response of the North Atlantic Treaty Organisation (NATO), Xinhua news agency reported.

"Our forces are not and will not be engaged in the conflict with Russia in Ukraine, our forces are not going to Europe to fight in Ukraine but defend our NATO allies and reassure those allies in the east," he reiterated, adding that NATO will convene a summit "on Friday".

A senior US defense official said in a statement on Thursday afternoon that the Pentagon had ordered the deployment to Europe of nearly 7,000 additional service members and that they are expected to "depart in the coming days".

The troops, the official added, will deploy to Germany to reassure NATO allies, "deter" Russia's military operations and be prepared to support a range of requirements in the region.

Biden also addressed concerns that oil prices may further go up as a result of US sanctions against Russia.

"We've been coordinating with major oil-producing and consuming countries toward our common interest to secure global energy supplies," he said.

"The US will release additional barrels of oil as conditions warrant."

The announcement was made hours after leaders of the Group of Seven (G7) countries met virtually to coordinate their responses to Russia's military actions in Ukraine.

The US President tweeted that he and his G7 counterparts had agreed to move forward on what he called "devastating packages of sanctions and other economic measures" against Russia.

Earlier on Thursday, he convened a meeting of the National Security Council in the White House Situation Room to discuss the latest developments in Ukraine.

Russian President Vladimir Putin authorised "a special military operation" in Donbas on Thursday and Ukraine confirmed that military targets across the country were under attack.

In a televised speech, Putin said the "plans do not include the occupation of Ukrainian territories" and that Russia is "not going to impose anything on anyone by force".

Russia's move, he added, is in response to "fundamental threats" of NATO which has expanded to eastern Europe and brought its military infrastructure closer to Russian borders.

Russian Foreign Minister Sergei Lavrov on Thursday said the US and NATO have broken their commitments, continuously expanded eastward, refused to implement the new Minsk agreement, and violated the UN Security Council Resolution 2202.

Ukrainian President Volodymyr Zelensky on Thursday said Kiev decides to sever diplomatic relations with Moscow.