The number of U.S. organizations designated by the Southern Poverty Law Center (SPLC) as hate groups has risen 20 percent in just three years, the law center said Tuesday.

A study from the SPLC found that 954 hate groups were operating in the United States in 2017, an increase of 4 percent from the year before and up one-fifth from 2014.

Black nationalist hate groups experienced the most substantial growth in 2017, which the SPLC credits to a backlash against President Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE from groups related to the Nation of Islam. Black nationalist groups surged from 193 organizations in 2016 to 233 chapters in 2017.

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Other substantial growth in the U.S. came among neo-Nazi organizations, which grew from 99 groups in 2016 to 121 in 2017, while anti-Muslim groups also experienced sharp growth from the year before. One hundred and fourteen anti-Muslim groups were operating in the U.S. last year, compared to 101 the year before.

In a statement accompanying the report, SPLC Intelligence Project Director Heidi Beirich warned that Trump is directly related to the increase.

“President Trump in 2017 reflected what white supremacist groups want to see: a country where racism is sanctioned by the highest office, immigrants are given the boot and Muslims banned," Beirich said.

“When you consider that only days into 2018, Trump called African countries ‘shitholes,’ it’s clear he’s not changing his tune. And that’s music to the ears of white supremacists," she added.

The greatest decline among the groups analyzed by the SPLC was among Ku Klux Klan-associated groups, which fell from 130 groups in 2016 to 72 last year.

The SPLC also recorded two "male supremacy" organizations as hate groups for the first time in 2017, calling out A Voice for Men, based in Houston, and Return of Kings, based in Washington, D.C.

A separate investigation from the SPLC found that 43 people have been killed and 63 others have been wounded by men associated in some form with the "alt-right" movement over the past four years. Seventeen of those deaths occurred last year.