Elderly survivors were gathering Saturday at the former Auschwitz death camp and political leaders warned that the Nazi genocide must continue to serve as a warning as the world marked International Holocaust Remembrance Day.

In Warsaw, Poland, U.S. Secretary of State Rex Tillerson paid his respects in a solemn ceremony at a memorial to the Jews who died revolting against German forces in the doomed Warsaw Ghetto Uprising of 1943.

Tillerson trailed two uniformed Polish military officers and readjusted a wreath underneath the monument, a hulking structure located in what was once the Warsaw Ghetto.

The head of Warsaw’s Jewish community read a prayer and Tillerson made brief remarks about the importance of not forgetting the horrors of the Holocaust.

“On this occasion it reminds us that we can never, we can never, be indifferent to the face of evil,” Tillerson said.

“The western alliance which emerged from World War II has committed itself to the assuring the security of all, that this would never happen again,” he said. “As we mark this day in solemn remembrance, let us repeat the words of our own commitment: Never again. Never again.”

His words came amid signs in Europe and beyond that ultra-nationalism and extreme right-wing groups are on the rise.

In Germany and Austria, the nations that perpetrated the killing of 6 million Jews and millions of others during World War II, far-right parties with their roots in the Nazi era are gaining strength. The anti-migrant, anti-Muslim AfD party won seats in the German parliament for the first time last year, while in Austria the nationalist, anti-migrant Freedom Party is in the government.

Both parties have had issues with members making anti-Semitic remarks.

Even Poland — which was occupied and terrorized by Hitler’s regime — was convulsed this week by revelations of a fringe neo-Nazi group that honors Hitler. Other ultranationalist parties that espouse anti-Jewish and anti-Muslim views seem increasingly emboldened as well.

In Europe, that support is partially a backlash to the large influx of mostly Muslim migrants to Europe that peaked in 2015.

Some of those migrants, especially from Arab countries, have brought their own brand of anti-Semitism with them.

In Germany, many Jews have reported feeling threatened by anti-Semitism — both from native far-right groups and from Arabs — and Jewish institutions across the country have increased security.

Meanwhile, Muslim immigrants have been the target of German far-right attacks or threats.

Hanni Levy, a 93-year-old Holocaust survivor from Berlin, criticized anti-migrant hatred during a speech at a Greens party convention in Hannover.

“In the past, the Jews were found guilty of everything. Today it’s the refugees,” said Levy, who survived thanks to the Germans who hid her. “One should never forget how difficult it is to leave behind everything just to survive.”

German Chancellor Angela Merkel marked the day by addressing the rising anti-Semitism in her weekly Saturday podcast.

She said that schools, which already teach about the country’s Nazi past, need to work harder at that especially so immigrant students from Arab countries will not “exercise anti-Semitism.”

She called it “incomprehensible and a disgrace that no Jewish institution can exist without police security —whether it is a school, a kindergarten or a synagogue.”

Commemorations were set to take place on Saturday after dusk, after the end of the Jewish Sabbath, to mark the 73rd anniversary of the liberation of Auschwitz, located in southern Poland.

The United Nations recognized January 27 as International Holocaust Remembrance Day in 2005.

(AP)