Supporters of the bizarre QAnon conspiracy theory were among the thousands of people who turned out to see President Donald Trump in Grand Rapids, Michigan, on Thursday.

Photos — including one tweeted by the president — show supporters holding aloft signs with Q Anon slogans.

QAnon adherents believe that Trump is out to take down an elite "deep state" child abuse ring.

Trump on Thursday hailed victory over the "deep state" in his first rally since Special Counsel Robert Mueller's report was submitted.

Supporters of the QAnon conspiracy theory were out in force at President Donald Trump's rally in Michigan on Thursday, where the president hailed victory over a "deep state" of officials he claims is out to topple him from power.

Footage taken at the rally in Grand Rapids — where Trump claimed that Special Counsel Robert Mueller's report exonerated him from accusations of collusion — showed thousands of supporters lining up to get into the event, many wearing clothing emblazoned with "Q" and shouting QAnon slogans.

NBC News reporter Ben Collins, who posted the video, tweeted: "I've been covering Qanon for a year, and the amount of pro-Q people in this video from yesterday's Trump rally line in Grand Rapids is absolutely shocking."

In a picture of the rally tweeted by Trump himself, one supporter appears to hold aloft a "Q" sign amid a sea of signs reading "jobs."

On social media, supporters of the conspiracy posted pictures of themselves at the event, while others posted images showing themselves tuning in to watch the rally from home.

George Conway, a Republican attorney and prominent Trump critic, tweeted that the number of QAnon adherents attending the Grand Rapids rally was "jaw-dropping."

Read more: The pro-Trump conspiracy theory known as 'QAnon' has moved from the fringes of the internet to feature prominently at Trump rallies

Trump at his rally in Grand Rapids, Michigan, on Thursday. Scott Olson/Getty Images

What is QAnon?

The QAnon conspiracy emerged on messaging boards 4chan and 8chan in late 2017, and has spread among a fringe of supporters of the president.

They believe that a top government official, codenamed Q, is responsible for a series of cryptic clues left on the messaging boards — with a large and obsessive online following devoted to unraveling them.

Supporters believe that the clues expose a "deep state" plot by intelligence officials, senior Democrats and Hollywood stars running a secret child abuse ring.

They also claim that Trump and Mueller are actually working together to break up the elite child abuse ring, and that Mueller's probe into the Trump campaign's ties to Russia is just cover.

A composite image of Trump and Special Counsel Robert Mueller, who completed his report on the Trump campaign's ties to Russia last week. AP/AP

It's not just grassroots supporters of the president, but celebrities and social media activists who have been gripped by the conspiracy.

Prosecutors allege QAnon has inspired violent plots. A man arrested in a self-armored truck packed with weapons near Arizona's Hoover Dam last July was allegedly obsessed with the conspiracy.

At Thursday's rally, Trump singled out the "deep state" as one of the enemies who had unsuccessfully sought to derail his presidency with allegations of collusion — in what could be interpreted as a nod to his more conspiratorially-minded supporters.

Read more: Trump escalates calls for revenge over the Mueller report, as supporters chant 'lock them up' at wild political rally

Trump also boasted to his supporters that Mueller's report showed the plots by the "deep state to overturn the results of the 2016 election have failed."