The United States targeted Russian banks and elites with a new round of sanctions, including banning Americans from investing in Russia, in response to what President Joe Biden condemned as "major war crimes" by Russian forces in Ukraine.

The new sanctions hit Russia's Sberbank, which holds one-third of Russia's total banking assets, and Alfabank, the country's fourth largest financial institution, U.S. officials said. But energy transactions were exempted from the latest measures, they said.

The United States is also sanctioning Russian President Vladimir Putin's two adult daughters, Russian Foreign Minister Sergei Lavrov's wife and daughter, and senior members of Russia's security council, the officials said.

"There's nothing less happening than major war crimes," Biden said in a speech to labor leaders, referring to the Ukrainian town of Bucha retaken from Russian forces, where bodies of civilians shot to death had been found.

"Responsible nations have to come together to hold these perpetrators accountable," he said. "And together with our allies and our partners, we're going to keep raising economic costs and ratchet up the pain for Putin."

Grim images emerging from Bucha include a mass grave and the bodies of people shot at close range, some of them bound, prompting calls for tougher action against Moscow and an international investigation. 

Russia, which says it launched a "special military operation" in Ukraine on Feb. 24, denies targeting civilians and said images of the deaths were a "monstrous forgery" staged by the West.

Wednesday's "full blocking sanctions" will freeze Sberbank and Alfabank's assets "touching the U.S financial system," the White House said.

Britain also froze Sberbank's assets, and said it would ban imports of Russian coal by the end of this year as part of a coordinated allied effort to "starve Putin's war machine."

Sberbank and Alfabank said the new sanctions would not have a significant impact on their operations.

Also among those sanctioned were Dmitry Medvedev, a former Russian president and ex-prime minister and one of Putin's closest allies. Others included Russian Prime Minister Mikhail Mishustin and Justice Minister Konstantin Chuychenko.

Later on Wednesday, Biden signed an executive order that prohibited "new investment in the Russian Federation by a United States person, wherever located." This includes a ban on venture capital and mergers, officials said.

Even as new sanctions were rolled out, Ukrainian President Volodymyr Zelenskiy was critical of some in the West and said he could not tolerate "any indecisiveness."