President Joe Biden Friday called on US political leaders to denounce anti-Semitism, days after Donald Trump hosted a well-known Holocaust denier and the rapper Kanye West -- whose virulent outbursts culminated this week with praise of Adolf Hitler.

Biden's warning comes at a time of rising concern in the United States over a normalization of anti-Semitic discourse -- increasingly co-opted by a white supremacist fringe that was emboldened under the Trump presidency.

"I just want to make a few things clear: The Holocaust happened. Hitler was a demonic figure," Biden tweeted. "And instead of giving it a platform, our political leaders should be calling out and rejecting antisemitism wherever it hides."

"Silence is complicity," Biden added.

The US president spoke out the day after West -- who now goes by the name Ye -- was kicked off Twitter for incitement to violence, following a post showing a Nazi swastika interlaced with a Star of David.

That came on the heels of an unhinged interview with conspiracy theorist Alex Jones and the Holocaust denier Nick Fuentes, in which West -- a black mask completely covering his face -- ranted about the devil, professed his "love" of the Nazis and declared "I like Hitler."

The White House had previously condemned Trump for hosting both West and Fuentes at his Mar-a-Lago resort in Florida last week.

According to the Republican former president, West brought along several friends uninvited, one of them Fuentes -- a white supremacist and outspoken anti-Semite whose YouTube channel was permanently suspended in 2020 over hate speech.

West has spoken openly about his struggles with mental illness, and his erratic behavior has raised mounting concerns -- leading his commercial relationships to crumble one by one.

The one-time titan of fashion and music is not the only celebrity to have triggered an uproar with anti-Semitic content of late: the NBA star Kyrie Irving was recently suspended for linking to a movie condemned as anti-Semitic, for which he apologized.

White supremacist ideology

Unease about the spread of hate speech has been exacerbated by Elon Musk's decision to cut back moderation since he bought Twitter last month.

Data published Friday by the Anti-Defamation League suggested those fears may be founded: anti-Semitic tweets referencing Jews and Judaism surged by more than 60 percent in the two weeks following Musk's takeover -- in line with an overall rise in hate speech.

The rhetoric has been matched by a steady rise in hateful incidents directed at Jewish people.

The Anti-Defamation League found that reports of harassment, vandalism and violence against Jews reached an all-time high in the United States in 2021.

Two years earlier in 2019, the country was shocked by deadly shootings targeting synagogues in California and Pittsburgh.

In both cases, the attackers were part of a broader, internet-based far-right that espouses hate against Muslims, Black people, immigrants and Jews, and advocate for a Caucasian, Christian society based on European culture.

The twin attacks reinforced concerns that anti-Semitic hatred is increasingly a rallying point for America's resurgent white supremacists -- who received tacit encouragement from Trump's failure to unequivocally condemn their ideology.

Critics of the former president, including Republican rebels such as Liz Cheney, have accused the party under Trump's sway of enabling white supremacy and anti-Semitism.

And Biden himself, who says he left retirement to run for president after he heard Trump refusing to clearly denounce a neo-Nazi rally in Charlottesville in 2017, has spoken out repeatedly against an ideology that "tears at the soul" of the nation.