The foreign ministry’s comments came after reports that two plaques commemorating the victims of the 1940 Katyn Massacre of Poles had been removed from the NKVD’s former regional headquarters in the town of Tver, 180 km north-west of Moscow.
In a statement in Polish on its website, published on the day that marked the 75th anniversary of the end of the war in Europe, the foreign ministry in Warsaw said it protested against practices aiming to “blur memories about the era of terror in Russia.”
It added that it could not accept “attempts to relativize the history of World War II and the tragic Stalinist period”.
Meanwhile, Polish Deputy Prime Minister and Culture Minister Piotr Gliński said in an interview on Friday that the incident in Tver was a "very sad development" in Polish-Russian relations.
"This is sad, and we will certainly protest strongly," he added.
One of the plaques bore a bilingual, Russian and Polish, inscription, reading: “In memory of the POWs from the Ostashkov camp killed by the NKVD in Kalinin [now Tver]. A warning to the world,” according to public broadcaster Polish Radio’s IAR news agency.
Gliński told Polish Radio on Friday that the memorial disappeared following “pressure” in Russia “to dismantle the plaque, which speaks the truth about obvious and actual facts and is dedicated to the memory of the murdered Poles.”
Earlier, the Polish government-affiliated Institute of National Remembrance (IPN) lambasted what it described as “a new wave of efforts to cover up the traces of the Katyn crime by the authorities of present-day Russia.”
The head of the institute, Jarosław Szarek, told Polish Radio on Thursday that the removal of the plaques was part of “a new form of Russia’s historical policy.”
He added that, in presenting the history of World War II, “the Russian authorities are returning to the communist, Soviet-era narrative.”
Some 22,000 Polish prisoners of war and intellectuals were killed in the spring of 1940 on orders from top Soviet authorities in what is known as the Katyn Massacre.
Following the Soviet invasion of Poland in September 1939, thousands of Polish officers were deported to camps in the Soviet Union.
POWs from camps in Kozelsk, Starobelsk and Ostashkov as well as Poles held in prisons run by the Soviet Union's NKVD secret police were among those murdered in April 1940.