STORY: Ukrainian forces took back control of the small towns of Bucha and Irpin to the northwest of Kyiv in late March last year as Russian invasion forces abandoned an attempt to seize the capital.
"Russian evil will collapse right here in Ukraine and will never be able to rise again. Humanity will prevail,” Ukrainian President Volodymyr Zelenskiy said.
The leaders of Croatia, Slovakia, Slovenia and Moldova also attended the ceremony.
Slovakian Prime Minister Eduard Heger said that Slovakia will help Ukraine, "as much as we can and as fast as we can for you to become part of the European Union."
Russia's occupation of the town resulted in more than 1,400 deaths, including 37 children, Kyiv said. More than 175 people were found in mass graves and torture chambers and 9,000 Russian war crimes have been identified, it said.
International investigators are now collecting evidence in Bucha and in other places where Ukraine says Russian troops committed large-scale atrocities. Russia denies the allegations.
Fighting is still raging in the east and south of Ukraine, but for places like Bucha, hundreds of miles away from the fighting, the war is still felt with regular air raid sirens telling residents to take cover from air strikes that have caused sweeping power outages.