"The victims of the crime committed in the 1940s by Ukrainian nationalists were not duly commemorated, and the mass murder was not defined as genocide in accordance with the historical truth," said a resolution adopted by 432 lawmakers in the 460-seat parliament.
Ukraine has refused to recognise the crime as genocide and its President Petro Poroshenko today to expressed his "regret" over the Polish move, warning it could be used against his crisis-hit country.
The UPA's main objective was to win Ukraine's independence by ousting Nazi and later Soviet occupiers and to clear Poles from territories that were historically Ukrainian land.
The killing provoked bloody reprisals by Polish partisans grouped in the anti-Nazi and anti-Soviet Home Army (AK). They killed 20,000 Ukrainians.
Today's resolution also recognises these crimes saying: "Nor can one dismiss or downplay acts of Polish revenge on Ukrainian villages, during which civilian populations also perished."
Poroshenko, meanwhile, invoking the teachings of late Polish-born pope John Paul II, called on people to "forgive and ask for forgiveness" while cooperating in order to "determine all the facts of this tragic page of our joint history".
The so-called Volhynia massacre was shrouded in silence during the communist era of 1945-1989, with regime authorities in Warsaw wanting to maintain ties with Ukraine, a Soviet republic until 1991.
