Pope Francis on Sunday asked the world's 1.3 billion Catholics to stop for a moment of prayer and reflection on the 75th anniversary of the liberation of the Nazi death camp at Auschwitz and say "Never Again".
The pope mentioned Monday's anniversary during his weekly noon address and blessing to tens of thousands of people in St. Peter's Square.
"Indifference is inadmissible before this enormous tragedy, this atrocity, and memory is a duty. Tomorrow, we are all invited to stop for a moment of prayer and reflection, each one of us saying in our own heart: 'never again, never again,'" he said.
More than one million people, most of them Jews, were killed at the Auschwitz-Birkenau camp during World War Two. Overall, some six million Jews died in the Holocaust.
At Francis' orders, the Vatican in March will open its secret archives on the wartime pontificate of Pope Pius XII, a historic move that Jews have sought for decades.
Some Jews say Pius, who reigned from 1939 to 1958, did not do enough to help those facing persecution by Nazi Germany and turned a blind eye to the Holocaust. The Vatican maintains that Pius chose to work behind the scenes.
The pope's appeal to his own flock on Sunday comes amid a backdrop of rising anti-Semitism in Europe and the United States. Last week, Francis called the rise a "barbaric resurgence".
On Friday, anti-Semitic graffiti was found scrawled on the door of the home of a son of a Holocaust survivor in northern Italy.
The words "Juden Hier" (Jews Here) were written above a Star of David on the door, recalling the signs put on buildings in Nazi Germany to mark the homes and businesses of Jews.
Last month in eastern France, scores of Jewish graves were found desecrated in a cemetery, hours before lawmakers adopted a resolution equating anti-Zionism with anti-Semitism.
France has Europe's biggest Jewish community - around 550,000 - and anti-Semitic attacks are common, with more than 500 alone in 2018.
A global survey by the U.S.-based Anti-Defamation League in November found that anti-Semitic attitudes had increased in many places around the world and significantly in Eastern and Central Europe. It also found that large percentages of people in Eastern and Western European countries think Jews talk too much about the Holocaust.
Before he became pope and was still archbishop of his native Buenos Aires, Francis co-authored a book with his friend, Argentine rabbi Abraham Skorka.
In 2016, Francis visited Rome's main synagogue, in the former ghetto established by his predecessor Pope Paul IV in 1555 and where Jews were confined until the 19th century.