LONDON: British Prime Minister Boris Johnson made a video appeal to Russians on Tuesday, calling on them to share reports about "atrocities" committed by their troops in Ukraine, saying if people knew the truth they would not support the war.

The United States and European countries, including Britain, have accused Russia of war crimes after the release of graphic images of civilian deaths and mass graves in the Ukrainian town of Bucha, outside Kyiv, over the weekend.

Russia, which says it has launched a "special military operation" to "denazify" Ukraine, has rejected the allegations, saying they were part of a forgery to denigrate the Russian military.

"The Russian people deserve the truth, you deserve the facts," said Johnson, speaking partly in Russian, in his message published on Twitter.

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"The atrocities committed by Russian troops in Bucha, Irpin and elsewhere in Ukraine have horrified the world ... The reports are so shocking, so sickening, it's no wonder your government is seeking to hide them from you.

"Your president knows that if you could see what was happening, you would not support his war."

U.S. President Joe Biden has described Russian President Vladimir Putin as a war criminal in the wake of the grisly discoveries in Bucha, and the United States has said it will seek to build a war crimes case against the Russian leader.

Russia has said Biden's comments were unacceptable.

Johnson called for Russians to use Virtual Private Network (VPN) connections so they could access independent information about the war to find out for themselves.

"And when you find the truth, share it. Those responsible will be held to account. And history will remember who looked the other way," he said, adding in Russian: "Your president stands accused of committing war crimes. But I cannot believe he's acting in your name."