Russian President Vladimir Putin will not travel to a ceremony in Poland marking the 70th anniversary of the liberation of the Nazis' Auschwitz death camp because he hasn't been invited by the hosts, the Kremlin said Tuesday.

Putin's spokesman, Dmitry Peskov, was quoted by the Interfax news agency as saying that the president hasn't received any invitation and therefore will not attend the event later this month.

The organizers of the ceremonies, the Auschwitz Museum and the International Auschwitz Council, said there had been no specific invitations but donor nations contributing funds to the site, including Russia, had been asked if they were going to attend.

The situation is particularly awkward since the Nazi death camp was liberated by the Soviet troops and many of about 1.5 million inmates, most of them Jews, who died in Auschwitz were Soviet citizens.

The apparent reason lies in the Ukrainian crisis, which has badly strained ties between Russia and the West.

The United States and the European Union have imposed sanctions against Moscow over its annexation of Ukraine's Crimean Peninsula and support for a pro-Russia insurgency in eastern Ukraine. Poland has been one of the harshest critics of the Kremlin's policy, and relations between the two countries have grown increasingly tense.

Putin did attend the ceremonies marking the 60th anniversary of the camps liberation, in 2005.

A spokesman for the Auschwitz Museum, Pawel Sawicki, told The Associated Press that no personal invitations were sent to anyone.

He said the organizers had informed embassies of the EU nations and the donor countries that the observances will be taking place on Jan. 27 and have asked them to reply whether they will be sending delegations and at what level.