Racially motivated extremists pose the most lethal domestic terrorism threats to the US, according to an unclassified intelligence report that warned that the threats could grow this year. The blunt assessment, in a report released by the Office of the Director of National Intelligence, echoes warnings made by US officials, including the FBI director, Christopher Wray, who testified earlier this month that the threat from domestic violent extremism was “metastasizing” across the country. Merrick Garland, the attorney general, has also described it as a top priority as his justice department works to prosecute hundreds of people who participated in the mob attack on the US Congress in January. The riot laid bare the threat posed by domestic extremists and led Joe Biden to assign his intelligence officials the task of studying the scope of the problems. A brief and unclassified summary of that threat assessment was made public Wednesday; a full classified report was presented to the White House and Congress. “Today’s report underscores how we face the greatest threat from racially or ethnically motivated violent extremists, especially white supremacists, and militia violent extremists,” said the Democratic representative Adam Schiff of California, the chair of the House intelligence committee. Intelligence officials said in their assessment that extremists seen as risks for violence are motivated by a range of ideologies. Developments such as the anger over restrictions imposed during the coronavirus pandemic and a belief in the debunked narrative that November’s presidential election was fraudulent “will almost certainly” spur additional violence in 2021, the report said. Numerous courts and Donald Trump’s own justice department upheld the integrity of the election. The report says the most lethal threat is presented by racially motivated violent extremists, who officials say are most likely to conduct mass attacks against American civilians, and militia groups, who are seen as likely to target law enforcement and government officials. The threat from militias increased in 2020 and is expected to increase again this year, according to the report’s summary. The report says white supremacists display what officials say is “the most persistent and concerning transnational connections”. Other domestic extremist categories that concern government investigators include animal rights and environmental activists, anti-abortion protesters, anarchists and people who call themselves sovereign citizens who “believe they are immune from government authority and laws”. Earlier on Wednesday Anti-Defamation League (ADL) said that distribution of white supremacist propaganda nearly doubled across America in 2020, with 5,125 reported incidents of racist, antisemitic and other hateful messages. The ADL said that 2020 had the “highest level” of cases of such propaganda since it started monitoring the phenomenon – an average of about 14 cases daily. The reports came hours after a gunman fatally shot eight people at several Atlanta-area massage parlors – six of the victims killed were of Asian descent, and seven were women – spurring fears the spree was racially motivated. The shootings were carried out amid an increase in anti-Asian bigotry across the US, which has included harassment and physical attacks.