WARSAW, Poland, Jan. 27 (UPI) -- People around the world commemorated Holocaust Remembrance Day Sunday on the 63rd anniversary of the Auschwitz concentration camp liberation in Poland.

A ceremony was held at the camp itself, and the governments of other countries observed moments of silence, Polish radio reported.

The remembrance is bittersweet, because only about 8,000 people were liberated, Polish radio said. Most of the camp's 56,000 inmates had already been moved to Germany in a death march that killed thousands.

An empty tram will run through what was formerly Warsaw's Jewish district, and additional activities will take place Monday, including a ceremony in front of the 1942 Warsaw Ghetto uprising memorial with state officials, organizations and youth.

The holiday was officially sanctioned by the United Nations in 2005.