The European Union is mobilizing its economy to make Russian President Vladimir Putin "pay a heavy price," European Commission President Ursula von der Leyen said on Friday in a visit to the Kyiv suburb of Bucha after it emerged that atrocities were committed there as Russian troops retreated recently.

"It was important to start my visit in Bucha. Because in Bucha our humanity was shattered," von der Leyen tweeted. "My message to Ukrainian people: Those responsible for the atrocities will be brought to justice. Your fight is our fight."

Saying that Russia will decay as Ukraine marches toward a European future, von der Leyen said it was right to suspend Moscow from the U.N. human rights council.

"Today we are here to give Ukraine first positive step toward EU membership."

Ukraine blames Russian troops for the slaying of hundreds of residents. Moscow denies involvement and says images that emerged over the weekend are staged, but has not presented any evidence for this claim.