Warsaw (AFP) - The Russian ambassador to Poland has alleged that Warsaw was partly to blame for World War II, prompting a storm of protest in the country which claims to be its greatest victim.

Sergei Andreev accused Poland -- which lost the highest proportion of its population in the conflict -- of "blocking the creation of an anti-Nazi coalition" which made it "co-responsible for World War II".

The ambassador also justified the Soviet invasion of Poland after Hitler and Stalin secretly agreed to divide up the country between them, as necessary to "guarantee the security of the Soviet Union".

And he said the Soviet decision to crush the Polish resistance as the war ended was motivated by the need to have a "friendly country at its borders".

But Warsaw responded angrily Saturday, saying Andreev's comments were highly damaging to relations between the neighbours, already strained by the conflict in Ukraine.

"The narrative presented by the highest official representative of the Russian state in Poland challenges historical truth and invokes some of the most mendacious interpretations of events, as resorted to during Stalinist and communist years," the foreign affairs ministry said in a statement.

Polish Foreign Minister Grzegorz Schetyna said that he would summon the Russian ambassador on Monday.

Warsaw also strongly objected to the ambassador's attempt to justify "the anti-Polish actions by the Soviet 'liberators'... in the arrest, deportation, and execution of Poles.

"We regard this as a lack of respect for the memory of victims of NKVD (secret police) crimes, perpetrated on the orders of the highest Soviet authorities," the statement added.

Up to six million Poles -- more than three million of them Jews -- were killed in WWII, more than a sixth of the country's pre-war population.

Asked about the Russian ambassador's comments, Polish Prime Minister Ewa Kopacz replied: "Even children in Poland know that neither Ribbentrop nor Molotov were Polish" -- a reference to the secret pact between the German and Soviet foreign ministers that set the war in motion by carving Poland and the Baltic states up between them.

More than 200,000 Polish soldiers were sent to camps in Siberia after the Red Army invaded Poland in September 1939, with nearly 22,000 of their officers massacred mostly at Katyn. Moscow blamed the Nazis for the atrocities until the fall of the Berlin Wall in 1989.

Several hundred thousand Poles considered "enemies of the people" were also transported to Soviet prison and work camps, with many perishing alongside imprisoned Polish soldiers from cold, hunger and overwork.