Released at last: the Katyn execution order signed by Stalin

Russia made public for the first time yesterday documents relating to the 1940 execution of 22,000 Polish officers by the Soviet NKVD secret police, including an order signed by dictator Joseph Stalin.

President Dmitry Medvedev released the material in the latest of a flurry of gestures of solidarity with Warsaw since Polish President Lech Kaczynski, his wife and 94 officials were killed on 10 April in a plane crash on their way to a ceremony commemorating the Katyn massacre in western Russia.

Russia's Federal Archive Service, or Rosarkhiv, published on its website scanned photos of several documents, including a 5 March, 1940, note from NKVD head Lavrenty Beria – signed by Stalin and three other members of the Soviet Politburo – ordering the execution of Polish "nationalists and counter-revolutionaries".

Mr Medvedev described the publication as a "duty". "Let people see it, let them know who made the decision to kill the Polish officers," he said during a trip to Copenhagen. "It's all there in the documents. All signatures are there, all the faces are known."

The Russian President added that he had ordered a number of Katyn documents still in Russia's hands to be passed to Warsaw.

Katyn is an enduring symbol for Poles of their suffering at Soviet hands. For decades, Moscow blamed the Nazis for the massacre and only acknowledged its responsibility in 1990, a year after the fall of communism in Poland. The Kremlin has resisted calls to brand the massacre genocide.

The published documents and their contents have been known to historians, politicians and families of those killed since the early 1990s but this is the first time most Russians have been able to see the scanned originals.

"Until now there still have been different perceptions, some doubts about who did it," said Vladimir Tarasov, deputy head of Rosarkhiv. "We wanted to dispel the doubts.

"Today's official publication is symbolic but important," said Yan Rachinski, one of the leaders of the human rights group Memorial which focuses on crimes of the Soviet period.

The publication is also a further sign that long-running tensions between Russia and Poland are easing. Mr Medvedev braved the closure of European airspace caused by a volcanic ash cloud on 18 April to attend Mr Kaczynski's funeral in Krakow and to tell Poles he hoped the tragedy could bring the two nations closer.

Last week, Russia's Supreme Court ordered the Moscow City Court to consider Memorial's appeal seeking declassification of a 2004 decision by military prosecutors to drop an investigation into the Katyn massacre.

"Let's hope that today's official publication on an official website is a step in that direction [of declassification]," Mr Rachinski said.

There are 183 volumes of documents relating to the 1990-2004 investigation, and 116 of them are still closed.

Mr Tarasov said no serious historian doubted the authenticity of the published documents. But Russia's opposition Communist Party still rejects them as false and insists the murder was committed by the Nazis. Last week, the party issued a letter to Mr Medvedev asking for a new investigation, referring to "insulting anti-Russian mourning ceremonies" at Katyn.