U.S. Secretary of State Antony Blinken on Thursday said he agrees with President Joe Biden that Russia has committed war crimes in Ukraine, adding that American experts are in the process of documenting and evaluating potential war crimes in Ukraine.

"Intentionally targeting civilians is a war crime," Blinken told reporters, adding that he finds it "difficult to conclude that the Russians are doing otherwise" after the destruction over the past few weeks.

"He’s a war criminal," Biden recently said of Putin as he left an unrelated event.

It’s the sharpest condemnation yet of Putin and Russian actions by a U.S. official since the invasion of Ukraine.

In a statement, the Kremlin described Biden's remarks as "unacceptable and unforgivable."

While other world leaders have used the words, the White House had been hesitant to declare Putin’s actions those of a war criminal, saying it was a legal term that required research.

Russia's invasion of Ukraine, which began on Feb. 24, has drawn international condemnation, led to financial sanctions on Moscow and spurred an exodus of global firms from Russia.

At least 726 civilians have been killed and 1,174 injured in Ukraine since the beginning of the brutal invasion.

More than 3 million refugees have fled to neighboring countries, according to the United Nations.