(CNN) White supremacists were responsible for the majority of extremist killings in 2017 compared to other groups, according to a newly released report by the Anti-Defamation League.

Of the 34 people the league's Center on Extremism found were killed by domestic extremists last year, right-wing extremists killed 20 people, with 18 of those killed by white supremacists, it said in the report released Wednesday.

"Extremism in any form is an issue. Foreign born, politically minded extremism or racially focused extremism. What the data tells us in the past 10-plus years it is far right-wing extremism, white supremacists and their ilk that are responsible for more extremist-related murders than any other group," said Jonathan Greenblatt, CEO of the Anti-Defamation League.

Last year was the fifth deadliest for extremist violence since 1970, when the ADL began tracking these types of crimes.

"Concretely it confirms extremists feel emboldened in the current environment. Right-wing extremists in particular were responsible for nearly 60% of extremist-related fatalities last year," Greenblatt said, "The data lays bare that this is not an exaggeration, as some would try to paint it."

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