Extreme right wing movement gains momentum in Europe, echoes heard around the world In Europe, some ultra-conservatives say their national identity is at risk.

 -- Thousands of right wing nationalists recently descended upon what was supposed to be a celebration of Poland’s independence day in Warsaw. Official ceremonies and patriotic songs were drowned out by demonstrators who chanted slurs like, “Pure Poland, refugees get out.” Some even paraded signs that read, “White Europe” and “Clean Blood.”

This march represented one face of a growing nationalist movement that has swept across Europe. Emboldened by a surge in anti-immigrant sentiments following the refugee crisis, ultra-conservative rhetoric is now seeping out of the fringes and into the mainstream. Many in these movements say they are battling what they claim is a trend of multiculturism that is threatening the traditional identity and heritage of their countries.

Their message was amplified this week when President Donald Trump retweeted a string of inflammatory videos that purported to show violence being committed by Muslims.

The three videos Trump retweeted were originally shared by Britain First, an anti-Islam, ultranationalist party known for hate-filled incitement. Jayda Fransen, the group’s deputy leader, later tweeted another video, thanking Trump for sharing her tweets.

But condemnation came swiftly from Britain’s highest office. “I’m very clear that retweeting from Britain First was the wrong thing to do,” said Prime Minister Theresa May. "Britain First is a hateful organization. It seeks to sow division and hate and mistrust in our communities.”

Fransen argues her movement is not based on hate, but on what she says are the feelings of ordinary citizens.

“You’re seeing a side of politics that has actually been on the back foot for a long time and that is the patriotic, common sense, everyday man that’s saying… ‘I live in the UK. I wish I’d be put first before immigrants,’” Fransen told ABC News’ Nightline.”

One of the videos shows what Fransen described in her post as a “Muslim migrant” attacking a “Dutch boy on crutches.” However, Dutch authorities clarified that the attacker was not a Muslim migrant; the embassy of the Netherlands later tweeted to President Trump that the attacker was in fact Dutch, saying, “facts do matter.”

The White House denied the President was pushing anti-Muslim propaganda when he retweeted the video and instead, made a case for national security.

“The threat is real, and that is what the President is talking about, is the need for national security, the need for military spending, and those are very real things, there’s nothing fake about that,” said White House Press Secretary Sarah Huckabee Sanders.

In Graz, Austria, ABC News’ “Nightline” recently met Luca Kerbl, the 26-year-old head of a nationalist group who call themselves identitarians.

Kerbl says he estimates there are 300 members of his group in Austria. They organize public stunts to spread their ideas beyond their circle. The stunts, he says, don’t often draw big crowds; but their goal is to have the photos and videos reach many more online.

For example, they recently set up papier-mâché dolls, which they dubbed multicultural zombies, on the steps of the Green Party headquarters in their area. They said their aim was to point out that members of the Green Party blindly followed a multicultural policy.

Kerbl insists his views are not bigoted. “I don’t have a feeling of supremacy because I’m white,” Kerbl told “Nightline.” “Christians and Muslims have the same god. They just [fight] each other in the belief of, ‘Mine is the better one.’”

“It’s my own culture. It’s the culture of my parents, of my uncles,” Kerbl added. “We have a duty anyway to keep going on.”

In Budapest, Hungary, “Nightline” met Daniel Friberg, a leading figure of the Swedish Right. Earlier this year, Friberg partnered in a web site venture with Richard Spencer, the self-proclaimed white nationalist and one of the most recognizable faces of the so-called American alt-right movement.

Friberg also founded Arktos, which is said to be the world’s largest distributor of far right literature. Much of the literature translated into dozens of languages and distributed around the world.

“This is a global phenomenon. And [the] American alt right have [been] inspired by the new right from France and Germany and Belgium especially, the identitarian movements all across Europe,” Friberg told “Nightline.”

Friberg said he believes “mass immigration and the great replacements” is what is currently wrong with Western politics.

“I know that we are [being replaced] because I know how to read statistics,” Friberg said. “People of childbearing age. Forty-seven percent of the segments are already non-European in Sweden. If that is not a replacement I don't know what is.”

Friberg claims there is one important difference between the nationalist movements in the U.S. and in Europe.

“In Europe, we don’t use the term whites for obvious reasons. That’s not people’s primary identity, right. People identify us as a Swede,” he said. “For a good reason, because white and black in the U.S. is kind of a household word… We use the word European and non-European because it makes more sense for us.”

But Joe Mulhall, a senior researcher from the British Hope Not Hate campaign says there are more troubling undertones masked by the immigration argument.

“They think that that's a message that will sell and that will work and perhaps they’re correct. There’s high levels of concern around those issues in Europe,” Mulhall told “Nightline.” “I think we have to look at actually what the Identitarians are talking about… Their ideas are fundamentally rooted in European fascist thought. They’re racist, Islamophobic, often they’re still extremely anti-Semitic, homophobic. A huge strain of these new movements are anti-feminist, anti-LGBT rights. There's a whole package here about what these groups are propagating. That goes well beyond saying it's just about levels of immigration.”