What is Antifa?

Anti-fascist counter-protesters wait outside Lee Park to hurl insults as white nationalists, neo-Nazis and members of the "alt-right" are forced out after the "Unite the Right" rally was declared an unlawful gathering August 12, 2017 in Charlottesville, Virginia. As protests over George Floyd's death spread across the country, officials have blamed the violent nature of some demonstrations on members of a controversial group known as Antifa. (Chip Somodevilla/Getty Images)
Anti-fascist counter-protesters wait outside Lee Park to hurl insults as white nationalists, neo-Nazis and members of the "alt-right" are forced out after the "Unite the Right" rally was declared an unlawful gathering August 12, 2017 in Charlottesville, Virginia. As protests over George Floyd's death spread across the country, officials have blamed the violent nature of some demonstrations on members of a controversial group known as Antifa. (Chip Somodevilla/Getty Images) (Getty Images)

(CNN) -- As protests over George Floyd's death spread across the country, officials have blamed the violent nature of some demonstrations on members of a controversial group known as Antifa.

Speaking at the Kennedy Space Center on Saturday, President Donald Trump said "the violence and vandalism" seen across the country "is being led by Antifa and other radical left-wing groups who are terrorizing the innocent, destroying jobs, hurting businesses and burning down buildings."

The President did not provide any evidence for his assertion.

President Trump tweeted Sunday that the United States will designate Antifa as a terrorist organization, even though the US government has no existing legal authority to label a wholly domestic group in the manner it currently designates foreign terrorist organizations.

Current and former government officials say it would be unconstitutional for the US government to proscribe First Amendment-protected activity inside the US based on simple ideology. US law allows terrorist designations for foreign groups since belonging to those groups doesn’t enjoy the same protections.

National Security Adviser Robert O'Brien echoed Trump's comments on CNN's "State of the Union" Sunday morning, telling Jake Tapper that the violence "is being driven by Antifa."

CNN has not independently verified whether the group is involved in recent protests.