Katyn massacres of 20,000 Poles were ordered by Stalin, Russia admits

The 1940 massacre of around 20,000 Polish officers and other prominent citizens in western Russia by Soviet secret police has long soured relations between the two countries. President Dmitry Medvedev will visit Poland in early December.

Soviet propaganda for decades blamed the killings on the Nazis but post-Soviet Russia previously acknowledged they were carried out by the People's Commissariat for Internal Affairs, or NKVD – Stalin's much-feared secret police.

The statement passed by the state Duma appears aimed as a step towards Russia definitively breaking with its Soviet legacy.

Some observers have expressed alarm in recent years that Russia may be quietly rehabilitating Stalin. Last year, a quote praising Stalin was restored to the decoration of one of Moscow's busiest subway stations; this year, Moscow's mayor proposed allowing posters depicting Stalin as part of the annual celebrations of the defeat of Nazi Germany.

The chairman of the Duma's foreign relations committee, Konstantin Kosachev, said according to the news agency ITAR-Tass: "This historic document is important not only for Russian-Polish relations – much more it is important for us ourselves."

Russia has turned over scores of volumes of documents this year about Katyn to the Polish government.

The head of the Polish parliament's foreign affairs committee, Andrzej Halicki, said he considered the Duma's statement to be a breakthrough.

"I am happy that such a process of reconciliation and truth is taking place," he said. "It is the first such act that proves that our relations and discussions are sincere."