The recent mass shooting of Muslim worshippers in New Zealand was a devastating and tragic symptom of the growing threat posed by violent white supremacy in the U.S. and across the world, experts say.

The death toll from the attack rose to 50 on Sunday. A 28-year-old Australian described by officials as a "right-wing extremist terrorist" has been charged with murder.

Brenton Harrison Tarrant appeared to post — and email —a lengthy manifesto before the attack detailing his white-supremacist worldview and claiming inspiration from Charleston church shooter Dylann Roof to Norwegian terrorist Anders Behring Breivik.

The manifesto also makes a brief reference to President Donald Trump.

“Were/are you a supporter of Donald Trump?” was one of the questions he posed to himself. His answer: “As a symbol of renewed white identity and common purpose? Sure. As a policy maker and leader? Dear god no.”

The White House immediately denounced the connection and Trump was among the many world leaders to condemn the shooting, but he faced criticism for downplaying the broader threat posed by white supremacists.

“I think it’s a small group of people that have very, very serious problems,” Trump said Friday when asked whether he thought it was a rising issue.

Trump's statement contradicts the warnings of his own administration.

GROWING THREAT

The FBI and the Department of Homeland Security warned in a 2017 intelligence bulletin that white supremacist groups had carried out more attacks in the U.S. than any other domestic extremist group over the past 16 years. And officials believe they are likely to carry out more.

The bulletin’s findings appear to correspond with independent data.

In January, for example, the New York-based Anti-Defamation League said domestic extremists killed at least 50 people in the U.S. in 2018, up from 37 in 2017. “White supremacists were responsible for the great majority of the killings, which is typically the case," the group wrote.

Between 2008 and 2016, far-right plots and attacks outnumbered Islamist incidents inspired by groups such as ISISby almost 2 to 1, according to an independent database compiled by the Investigative Fund at the Nation Institute.

The number of hate groups operating across America also rose to a record high of 1,020 in 2018, according to the Southern Poverty Law Center. The vast majority of those groups adhere to some form of white supremacist ideology, the center said, though they also include anti-LGBTQ and black nationalist groups, among others.

Since 2016, America has seen 11 people shot dead in a Pittsburgh synagogue; a protester mowed down by a white nationalist in Charlottesville, Virginia, and a coast guard officer prosecutors say was arrested before his violent white nationalist beliefs could lead him "to murder innocent civilians on a scale rarely seen in this country."

On Friday, it was reported that Cesar Sayoc, the Florida man charged with sending more than a dozen pipe bombs to prominent critics of the president, is expected to plead guilty next week.

In a testimony submitted to Senate hearing on homeland security last year, FBI director Christopher Wray said of the 1,000 active investigations into domestic terrorism, the agency "is most concerned about lone offender attacks, primarily shootings, as they have served as the dominant mode for lethal domestic extremist violence."

"We anticipate law enforcement, racial minorities, and the U.S. Government will continue to be significant targets for many domestic extremist movements,” he added.

'BOTH SIDES' OF THE ATLANTIC

Friday was not the first time Trump has equivocated in the face of white nationalism.

After the violence in Charlottesville he said there were “very fine people on both sides.”

His travel ban against people from several mostly Muslim-majority countries has also drawn widespread criticism.

On Sunday the president tweeted his support for Fox News host Judge Jeanine Pirro, whose show did not air Saturday night after she questioned the loyaltyof Rep. Ilhan Omar, D-Minn., because of her Muslim beliefs and headscarf.

Bring back @JudgeJeanine Pirro. The Radical Left Democrats, working closely with their beloved partner, the Fake News Media, is using every trick in the book to SILENCE a majority of our Country. They have all out campaigns against @FoxNews hosts who are doing too well. Fox ..... — Donald J. Trump (@realDonaldTrump) March 17, 2019

....must stay strong and fight back with vigor. Stop working soooo hard on being politically correct, which will only bring you down, and continue to fight for our Country. The losers all want what you have, don’t give it to them. Be strong & prosper, be weak & die! Stay true.... — Donald J. Trump (@realDonaldTrump) March 17, 2019

"The president is not a white supremacist. I'm not sure how many times we have to say that," acting White House chief of staff Mick Mulvaney said on "Fox News Sunday."

But the rise of white supremacy is not exclusive to the United States and experts say it has been allowed to grow, thanks to a much broader culture.

"I think it’s connected to how emboldened they've become and how much legitimization and affirmation they get from the mainstream media, social media and far-right politicians," Aaron Winter, senior lecturer in criminology at the University of East London, told NBC News.

There had been a period in the U.S. and other Western countries when the popular notion was that racism was a thing of the past only held on to by fringe individuals, Winter said.

But since 2009, anti-Muslim and anti-immigrant perspectives and policies have widely increased, in part as a response to the election of President Barack Obama, the global financial crisis and a string of international conflicts.

The public acceptance of these views can in turn rouse people who are inclined to take extreme action, Winter said.

Winter pointed to Trump's election campaign, the U.K.'s Brexit campaign and Australian politics as notable examples.

"We — and that includes policymakers and the law enforcement community, in particular — must begin to view what we call 'domestic terrorism' through a global lens, just as we do the threat of groups like ISIS," said the SPLC's president Richard Cohen on Saturday.

"Because the growing white supremacist movement represents a clear and present threat to democracies across the world."

In Britain, the government's counter-extremism strategy released figures showing that the number of individuals flagged for risk of extremism who had right-wing ties was up 36 percent in 2017-2018 compared to the previous year. It was a sharp contrast to the number of people flagged for being at risk of Islamic extremism, which had declined 14 percent in the same period.

Yet Winter said violence and threats by the far right in many Western countries have been largely overshadowed by fears of Islamist extremists.

"They only become the enemy within when they cause a problem for the mainstream or it becomes too loud to ignore," Winter said, pointing to a 2017 attack near a mosque in London that prompted condemnation by politicians.

But outrage from political leaders doesn't go far enough to solve the problem, he added.

"It doesn't matter if it's just a small number of people if, basically, the people who are making the policies and spreading the rhetoric are trying to say the same things about these target groups — Mexicans, Muslims, immigrants etc.," Winter said.