White supremacists posted more propaganda on college campuses for the third year in a row as they tried to recruit members, the Anti-Defamation League said Thursday.

Fliers and stickers with veiled white supremacist language or explicit racist messages were posted on public and private campuses across America. The groups that post them also frequently spread messages that were anti-Semitic and homophobic.

Some explicitly attacked minority groups including Jews, African Americans, Muslims, non-white immigrants and the LGBTQ community, according to the ADL, which monitors and campaigns against hate.

Other fliers continued the trend of efforts to deceptively promote American identity, the ADL said, by having no explicitly hateful message but linking to a website where racist content is posted.

The ADL documented 313 cases of white supremacist propaganda on college campuses, 7% more than it documented in the 2017-18 academic year, which was itself 77% higher than the incidents observed the previous year, according to the ADL's Center on Extremism.

More extremist propaganda was found on campus during the 2019 spring semester than in any preceding semester since 2016 when the ADL began tracking this kind of activity, it says.

The ADL tells CNN it believes that both students and non-students are responsible for the incidents. The group tracks the incidents from complaints from the community, social media postings and media reports.

"This data clearly demonstrates that white supremacists in the United States are emboldened by the current political and social climate," ADL CEO and National Director Jonathan Greenblatt said in a statement. "Our campuses and communities should be places for learning and development, not places for racists and bigots to propagate hate speech and search for potential recruits."

Where the incidents are happening

During the spring 2019 semester, 161 incidents of extremist propaganda were found on 122 campuses, according to ADL data. They were found on campuses in 33 states and the District of Columbia.

For the entire academic year: