Russian president Vladimir Putin will not attend the ceremony commemorating the 70th anniversary of the liberation of the Auschwitz-Birkenau concentration camp, a Kremlin spokesman revealed. 

Dmitry Peskov told AFP that the anniversary ceremony  was “not on the Russian president’s agenda,” without going into further detail. The Russian ambassador in Poland will represent the country. Putin’s absence is particularly significant, as the camp was liberated by Russian forces at the end of World War II.

Some political pundits have speculated that Putin’s failure to attend is a sign of deepening divisions between Russia and Europe, relating to Poland’s vocal criticism of Russia’s annexation of Crimea and the subsequent political destabilization of Ukraine.

The ceremony, which coincides with International Holocaust Remembrance Day on January 27, will be led by Polish president Bronislaw Komorowski. The Holocaust Museum didn’t send invitations, but notified forty three countries of the remembrance service. The heads of state whose attendance has been confirmed include the German president Joachim Gauck and the French president Francois Hollande. According to a list released by the Auschwitz Museum, the U.S. is yet to confirm the presence of a representative.

The Nazis killed approximately 1.1 million Europeans at Auschwitz-Birkenau between 1940 and 1945, including about 1 million Jews.