WARSAW, Poland — Jewish and Christian leaders prayed over the ruins of gas chambers at Auschwitz-Birkenau as some leaders warned Friday on International Holocaust Remembrance Day of rising xenophobic hatred against Jews and others, including Muslims.

Dozens of survivors gathered with political leaders and representatives of Poland's Jewish community at the site where Germany murdered about 1.1 million people during World War II, mostly Jews from across Europe, but also Poles, Roma, Soviet prisoners of war and others.

Poland's Prime Minister Beata Szydlo, who is from the Polish town where the Auschwitz memorial and museum is located, recalled the "destruction of humanity" and the "ocean of lost lives and hopes" in Oswiecim.

"It's an open wound that may close sometimes but it shall never be fully healed and it must not be forgotten," she said.

Dozens of Auschwitz survivors began a day of commemorations by placing wreaths and flowers at the infamous execution wall on the 72nd anniversary of the camp's liberation by Soviet soldiers. The United Nations recognized January 27 as International Holocaust Remembrance Day in 2005, and many commemorative events were taking place across the world on Friday.

"Tragically, and contrary to our resolve, anti-Semitism continues to thrive," U.N. Secretary-General Antonio Guterres said in statement made in New York Thursday, and which was read out at the U.N. headquarters in Geneva on Friday. "We are also seeing a deeply troubling rise in extremism, xenophobia, racism and anti-Muslim hatred. Irrationality and intolerance are back."

Guterres vowed to "be in the front line of the battle against anti-Semitism and all other forms of hatred."

In Germany, outgoing Foreign Minister Frank-Walter Steinmeier said his nation sticks by its obligation to take responsibility for the crimes committed by the Nazi regime of Adolf Hiltler.

Noting the political instability in the world today, Steinmeier said, "History should be a lesson, warning and incentive all at the same time. There can and should be no end to remembrance."

Steinmeier's statement came hours before he was due to hand over the post of foreign minister to the current economy minister, Sigmar Gabriel.

In Croatia, the Jewish community boycotted official commemorations, saying the country's conservative government is not doing enough to curb pro-Nazi sentiments there.

Community leader Ognjen Kraus, the coordinator of the Jewish communities in Croatia, said the decision was made after authorities failed to remove a plaque bearing a World War II Croatian pro-Nazi salute from the town of Jasenovac — the site of a wartime death camp where tens of thousands of Jews, Serbs and Roma perished.

Elderly survivors at Auschwitz, which today is a museum and partially preserved memorial, paid homage to those killed by wearing striped scarves to symbolize the uniforms prisoners were given when they arrived at the concentration camp.

They walked slowly beneath the notorious gate with the words "Arbeit Macht Frei" (Work Will Set You Free) and made their way as a group to the execution wall, where they lit candles and prayed.

Janina Malec, a Polish survivor whose parents were killed at the execution wall, described her yearly visit as a "pilgrimage" and told the PAP news agency that "as long as I live I will come here."

Frank Jordans in Berlin contributed.