White supremacists in the United States represent the “most persistent and lethal threat” of violent domestic extremists while China and Russia pose serious foreign concerns, according to a new study by the Department of Homeland Security.

“Ideologically motivated lone offenders and small groups pose the most likely terrorist threat to the Homeland, with Domestic Violent Extremists presenting the most persistent and lethal threat,” acting DHS Secretary Chad Wolf wrote in the department’s first-ever annual Homeland Threat Assessment, obtained late Monday by CBS News. “I am particularly concerned about white supremacist violent extremists who have been exceptionally lethal in their abhorrent, targeted attacks in recent years.”