The country on July 11 marked its National Day of Remembrance of Victims of Genocide by Ukrainian nationalists against Poles during World War II.
On the 81st anniversary of the tragic events, Poland's foreign ministry paid tribute to the victims of the wartime killings, known as the Volhynia Massacres.
"May we never again let prejudice sow division between our nations," the Polish foreign ministry said on social media.
Officials attended a series of commemorative events, including one at a Warsaw monument honouring those murdered during the Volhynia Massacres.
President Andrzej Duda said in a letter read out during the ceremony that the Poles and Ukrainians need to build their future relations "based on truth" in order to put their difficult past behind them.
The two neighbouring countries need truth, "even if it is a difficult truth, associated with suffering," Duda said, because "only truth can support the development of new and lasting relationships between both individual people and entire nations."
Ukrainian embassy officials took part in the commemoration on behalf of President Volodymyr Zelensky to honour those who lost their lives 81 years ago, news outlets reported.
The Volhynia Massacres were carried out between February 1943 and the spring of 1945 by the Ukrainian Insurgent Army (UPA) in Nazi German-occupied Poland, according to Poland’s National Institute of Remembrance (IPN).
Some 100,000 ethnic Poles in total were slaughtered in the 1940s by Ukrainian forces, according to some estimates.
On July 11, 1943, the day of the worst bloodshed, Ukrainian nationalists attacked 100 villages largely inhabited by Poles in what was then Nazi-occupied eastern Poland and is now western Ukraine.
The massacres were part of an operation carried out by the Ukrainian Insurgent Army (UPA), whose plan was to have a sovereign and nationally homogenous Ukraine after the war.
The Volhynia region, which was within Poland's borders prior to World War II, was first occupied by the Soviets in 1939, and then by the Nazi Germans in 1941.
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Source: IAR, PAP