The federal indictment of former US president Donald Trump has unleashed a wave of calls by his supporters for violence and an uprising to defend him, disturbing observers and raising concerns of a warlike atmosphere before his court appearance in Miami on Tuesday.

In social media posts and public remarks, close allies of Trump – including a member of Congress – have portrayed the indictment as an act of war, called for retribution and highlighted the fact that much of his base carries weapons. The allies have painted Trump as a victim of a weaponised Justice Department controlled by President Joe Biden, his potential opponent in the 2024 election.

The calls to action and threats have been amplified on right-wing media sites and have been met by supportive responses from social media users and cheers from crowds, who have become conditioned over several years by Trump and his allies to see any efforts to hold him accountable as assaults against him. Experts on political violence warn that attacks against people or institutions become more likely when elected officials or prominent media figures are able to issue threats or calls for violence with impunity.

The former president alerted the public to the indictment on Thursday evening in posts on his social media platform, attacking the Justice Department and calling the case “THE GREATEST WITCH HUNT OF ALL TIME”.

“Eye for an eye,” wrote Republican Representative Andy Biggs (Arizona), in a post on Twitter on Friday. His warning came shortly before the special counsel in the case, Jack Smith, spoke to the public for the first time since he took over the investigation of Trump’s retention of classified documents.

On Instagram, Trump’s eldest son’s fiancee, Kimberly Guilfoyle, posted a photo of the former president with the words, “Retribution Is Coming”, in all capital letters.

In Georgia, at the Republican state convention, Kari Lake, who refused to concede the Arizona election for governor in 2022 and who is an ardent defender of Trump, emphasised that many of Trump’s supporters owned guns.

“I have a message tonight for Merrick Garland and Jack Smith and Joe Biden – and the guys back there in the fake news media, you should listen up as well, this one is for you,” Lake said. “If you want to get to President Trump, you are going to have go through me, and you are going to have to go through 75 million Americans just like me. And I’m going to tell you, most of us are card-carrying members of the NRA.”