Russia has handed over to Poland a further batch of secret documents on the World War Two Katyn massacre of thousands of Polish nationals.
20 volumes of documents have been handed over, four months after a first batch of 67 volumes were given to Warsaw.
The documents include lists of prisoners of war, transcripts of interrogations, medical records, death certificates and forensic reports.
Poland requested the evidence as a way of shedding more light on the 1940 massacre of some 22,000 Poles, including thousands of military officers, in the Katyn forest and elsewhere.
For a long time Moscow blamed the Nazis for the killings, but in 1990 the then leader Mikhail Gorbachev accepted that his country was to blame.
Russian investigators finished a 14-year inquiry into the massacre in 2004, confirming the guilt of Soviet officials and the secret police.