Russia's lower house of parliament has condemned Joseph Stalin for the mass execution of Poles at Katyn during World War II.
The Duma declared that the Soviet dictator and other Soviet officials had ordered the "Katyn crime" in 1940.
In a stormy debate, Communist MPs opposed the declaration, some seeking to deny Soviet guilt. Last month the Communist Party described Katyn as "one of the greatest myths of the 20th century".
Soviet propaganda sought for decades to portray the massacre as the work of the Nazis, who overran Katyn after invading the Soviet Union ( now Russia) in 1941.
The BBC reports the truth was finally acknowledged in 1990, but the issue has continued to cloud relations between Russia and Poland.
The Duma said it hoped for "the beginning of a new stage in relations" with Poland "based on democratic values".
Russian President Dmitry Medvedev is to visit Poland early next month.
The actual number of Polish prisoners killed at Katyn and other Soviet sites is generally held to be about 22,000, including about 8000 military officers.
The declaration called for the massacre to be investigated further in order to confirm the list of victims. A judicial investigation in 2005 confirmed the execution of 1803.
The Duma also argued that Katyn was a tragedy for Russia too, as thousands of Soviet citizens were executed and buried in ditches there in the years 1936-38, a period of Soviet history known as the Terror.