Pope Francis has warned the threat of anti-Semitism is "still lurking" in Europe, during a brief trip to Hungary.
He was speaking after meeting Hungary's populist and anti-immigrant PM Viktor Orban, with whom he has stark differences on the issue of refugees.
Mr Orban has also been accused of an anti-Semitic stance, but he has said this is "simply ridiculous".
In a Facebook post, the PM said he had "asked Pope Francis not to let Christian Hungary perish".
Pope Francis' meeting with Mr Orban lasted about 40 minutes in the Museum of Fine Arts in Budapest.
In his address to Christian and Jewish leaders afterwards, Francis warned of "the threat of anti-Semitism still lurking in Europe and elsewhere".
He said: "This is a fuse that must not be allowed to burn. And the best way to defuse it is to work together, positively, and to promote fraternity."
Hungary has a large Jewish community - some 100,000 strong.
Mr Orban was criticised for his 2017 election campaign that included posters of Jewish financier George Soros, with the words "Let's not allow Soros to have the last laugh!" He rejected calls from the Jewish community to take them down.
On a visit to London, the PM denied any anti-Semitism, saying that Mr Soros was simply a rival who favoured migrant movement.
Mr Orban and the Pope certainly have divergent views on refugees and migration.
Some of the PM's supporters in Hungary, along with pro-Orban media, have in the past mocked the Pope as "anti-Christian" for his comments on helping refugees.
At a Mass later on Sunday, Pope Francis alluded to the issue, saying: "The cross, planted in the ground, not only invites us to be well-rooted, it also raises and extends its arms towards everyone."
"The cross urges us to keep our roots firm, but without defensiveness... My wish is that you be like that: grounded and open, rooted and considerate," the pope said.
Francis was celebrating Mass to mark the end of the Eucharistic Congress, which has attracted tens of thousands of Christians from around the world over the past week.
One worshipper, Eva Mandoki, 82, told Agence France-Presse: "We are not here for any politics, but to see and hear the Pope, the head of the Church. We can hardly wait to see him."
The Pope's whole Hungarian visit is expected to last only about seven hours, before he moves on to Slovakia for three days.
The brevity of his Hungary trip compared to Slovakia has raised speculation about what signals the Pope is trying to send.
One pro-Orban TV analyst said: "Pope Francis wants to humiliate Hungary by only staying a few hours."
The Vatican has called it a "spiritual trip" and Mr Orban said comparisons with Slovakia were "misleading". But some sources say the Vatican rejected offers of a longer stay.
The meeting between Viktor Orban, self-styled crusader against liberalism, and the liberal Pope passed peacefully, according to comments from the Vatican and the PM's office.
The role of the Church, protection of the environment and promotion of the family were among the topics discussed, said the Vatican.
The Pope later delivered a message of inclusion and fraternity to Christian and Jewish leaders, using the symbolism of the Chain Bridge across the Danube, currently undergoing repairs, to underline his message.
The opposition-run city council, meanwhile, welcomed Pope Francis in its own way, with quotes from his speeches. "The abuse of power wounds human dignity, which we cannot allow and must struggle against," read one, displayed prominently on posters around Budapest.
This is the Pope's first international trip since surgery this year.
In Slovakia, his visit aims to improve Catholic-Jewish relations and he will also meet members of Slovakia's Roma community.
Francis has visited dozens of countries since he became pope in 2013, although his travels have recently been affected by the spread of coronavirus.
Earlier this year, he made a historic four-day trip to Iraq.
In July, the 84-year-old spent 10 days in hospital while he received treatment for a colon problem.
He also suffers from a number of other health issues. He lost part of his right lung at the age of 21 and also suffers from a hip problem and sciatica, which causes pain that radiates from the lower back to the legs.