( CNN ) -- Russia 's lower house of parliament has approved a resolution recognizing that Josef Stalin 's regime was responsible for the 1940 massacre of more than 20,000 Polish officers , signaling a thawing of relations between Poland and Russia , state media reported . In a written statement , Poland 's Foreign Ministry said it welcomed the resolution titled `` Katyn Tragedy and Its Victims , '' adopted by the State Duma of the Russian Federation on Saturday . `` Acknowledging the Stalinist totalitarian regime 's accountability for this unprecedented massacre is the Russian Parliament 's important gesture , signifying that we are making progress on the way to reconciliation between our countries and peoples , '' said the statement . `` This gesture proves that there is no turning back from the truth-based dialogue between Poland and Russia , '' the statement said . Documents that had been stored in secret archives for years show that the `` massacre was committed on the direct orders of Stalin , '' a draft of the declaration says , according to the state-run RIA Novosti news agency . The masterminding of the Katyn Massacre has been a lingering , contentious issue between the two former communist nations . The World War II massacre , in which an estimated 20,000 Polish officers were murdered at point blank in the village of Katyn , has tainted Russian-Polish relations . The Duma 's Friday vote comes as Russian President Dmitry Medvedev prepares to travel to Poland in December . For decades , the Soviet government blamed the killings on Nazi Germany . In 1990 , Russia finally admitted to what many in Poland had long suspected : The Soviet Union secretly murdered as many as 22,000 Polish soldiers and civilians in the early days of World War II in an attempt to pre-emptively suppress a Polish rebellion against communist rule . That year , Russian prosecutors also launched a criminal case into the killings , but that case was closed in 2004 . Since then , the country has handed over some investigation files to Polish officials . This year , a 2007 film about the massacre aired on Russian television for the first time . But some Russian lawmakers say the issue is still in dispute . Communists , who opposed the declaration , claim German authorities actually executed the Polish soldiers . The party 's leader has dubbed attempts to blame Stalin part of `` Soviet history falsification '' as part of an `` ideological war , '' RIA Novosti reported . Former Polish President Lech Kaczynski was killed in a plane crash earlier this year when he was headed to a memorial at the massacre site . Kaczynski , 60 , had been traveling with a Polish delegation to Russia to commemorate the massacre 's 70th anniversary . His wife and several top military officials were also killed in the crash .
NEW : Poland welcomes the Germans , foreign ministry says . The mass execution of more than 20,000 Polish soldiers is a major diplomatic sticking point . A spokesman says the ` ` massacre was committed on the direct orders of Stalin '' and claim German authorities actually executed the Polish soldiers .