MOSCOW, April 7 (UPI) -- Russia gave Poland Thursday 11 volumes of once-secret papers from a massacre of 21,768 Poles during the Soviet invasion of Poland, a prosecutor's office said.
The declassified documents contain conviction and burial certificates of those killed in the April-May 1940 massacre in the Katyn Forest, near the western Russian city of Smolensk, and other data related to the massacre, the state-owned RIA Novosti news agency quoted the Russian Prosecutor General's office as saying.
Poland had no immediate public comment.
The Katyn massacre -- in which Polish nationals, including officers, police and civilians taken as prisoners of war were executed by the Soviet secret police -- remains one of the most painful issues in Russian-Polish relations.
A year ago Russian Prime Minister Vladimir Putin became the first Russian or Soviet leader to join Polish officials in commemorating the massacre's anniversary.
"We bow our heads to those who bravely met death here," Putin said April 7, 2010.
"In this ground lay Soviet citizens, burnt in the fire of the Stalinist repression of the 1930s; Polish officers, shot on secret orders; soldiers of the Red Army, executed by the Nazis," Putin said.
The first 67 volumes of documents held by Russia concerning the massacre were handed over to Polish President Bronislaw Komorowski last May. Another 20 were presented in September. Russian President Dmitry Medvedev handed over an additional 50 volumes in December.
The Russian Parliament in November approved a resolution directly blaming Soviet leader Joseph Stalin for the massacre and officially admitting the guilt of Soviet officials. The Soviet government had suppressed all information about the shootings, placing blame on Nazi soldiers.
Komorowski succeeded Lech Kaczynski as president last May after Kaczynski, his wife and 94 officials were killed in a plane crash in Smolensk en route to Katyn Forest to mark the massacre's anniversary.
Russia said Thursday it was waiting for a Polish report on a transcript of the black box flight recordings from the April 10, 2010, crash in thick fog. On Wednesday it said it provided Poland with documents on the crash.
A Commonwealth of Independent States aviation committee last October blamed the Polish pilot for trying to land in poor weather conditions.
Poland said Jan. 18 the Russian air-traffic controller had initially told the pilot he was "on course" when the plane was actually off course -- and gave the off-course warning 11 seconds too late.
