Russian President Vladimir Putin "seems to be isolated," and evidence appears to show he has punished top advisers for Moscow's poor military showing in Ukraine, U.S. President Joe Biden said Thursday.

Biden said "there's some indication" that Putin has either outright fired some of his advisers or put them under house arrest but said he does not yet want to "put too much stock in that at this time" due to a lack of "hard evidence."

The comments come one day after the U.S. declassified intelligence that indicates Putin is unaware of how poorly the Russian military is performing in Ukraine, as well as the significant strains being imposed on Russia's economy by Western-led sanctions.

The White House said it has information that "Putin felt misled by the Russian military" which resulted in "persistent tension" between Putin and his military brass.

White House spokesperson Kate Bedingfield told reporters that Russia's decision to invade Ukraine has "been a strategic error."

"So it is increasingly clear that Putin's war has been a strategic blunder that has left Russia weaker over the long term, and increasingly isolated on the world stage," she added.

Russia's war on Ukraine, which began Feb. 24, has drawn international outrage, with the European Union, United States and the United Kingdom, among others, implementing tough financial sanctions on Moscow.

At least 1,232 civilians have been killed in Ukraine and 1,935 injured, according to estimates by the United Nations, which noted the true figure is likely far higher.

More than 4 million Ukrainians have also fled to several European countries, with millions more displaced inside the country, according to the United Nations High Commissioner for Refugees.