Russian Prime Minister Vladimir Putin is in Poland for events Tuesday marking the 70th anniversary of the start of World War II as Russia fiercely denies blame in causing the war.

He plans to hold talks with Polish Prime Minister Donald Tusk and also meet with the prime ministers of the Netherlands, Finland, Bulgaria, Croatia, and Slovenia.

Writing in Poland's Gazeta Wyborcza newspaper, Mr. Putin condemned the 1939 Molotov-Ribbentrop treaty as immoral.

The pact secretly split the Baltics and parts of eastern Europe between the Soviet Union and Nazi Germany. Historians say it encouraged Germany to invade Poland on September 1, 1939, setting off the war.

Mr. Putin blamed other European countries for refusing to back the Soviet Union, leaving Moscow to face the threat of Nazi Germany alone.

But he also wrote that the 1940 massacre of thousands of Poles by Soviet security forces in the Katyn Forest was a crime and that Russia has a duty "to remove the burden of distrust and prejudice left from the past."

On Sunday, Russian President Dmitri Medvedev said anyone who tries to lay equal blame for the war on Nazi Germany and the Soviet Union is telling a "flat-out lie."

Some information for this report was provided by AFP.