Russians working for an ally of Vladimir Putin are waging an “information warfare” campaign to disrupt the 2018 midterm elections and discredit Robert Mueller’s Trump-Russia investigation, US authorities said on Friday.

The allegations were outlined by the FBI as a Russian woman accused of playing a senior role in the influence operation was charged with conspiring to interfere in the US political system.

Elena Khusyaynova, 44, is said to be the chief accountant for a $35m project orchestrated by Yevgeniy Prigozhin, an oligarch known as “Putin’s chef” who has already been charged by the US with interfering in the 2016 election.

Prigozhin’s team allegedly used social media and other web platforms to promote Donald Trump’s agenda and stoke conflict among Americans on divisive topics. Those included Mueller’s inquiry into whether Trump’s team colluded with Russian officials in an effort to swing the 2016 campaign.

Court filings in Virginia unsealed on Friday said that, as early as July 2017, the Russians were spreading online messages that Trump was the victim of a “witch-hunt” and that Mueller was a “puppet of the establishment” tied to Democrats whose investigation was “damaging to the country”.

Trump has repeatedly denounced Mueller’s inquiry in similar terms since then.

Christopher Wray, the director of the FBI, said in a statement the charges against Khusyaynova highlighted “threats to our democracy” from online propaganda campaigns.

The case, Wray said, “serves as a stark reminder to all Americans: our foreign adversaries continue their efforts to interfere in our democracy by creating social and political division, spreading distrust in our political system, and advocating for the support or defeat of particular political candidates.”

Prigozhin’s influence campaign, known internally as “Project Lakhta”, has allegedly been working to “inflame passions” on controversial news topics. The court documents contained multiple examples of the operation advocating for Trump’s agenda.

Russian operatives were allegedly directed to share a pro-Trump article from the rightwing conspiracy site InfoWars, along with messages that “fully support Donald Trump” and stating that “Trump once again proved that he stands for protecting the interests of the United States of America”.

The operatives were also told to push questionable research by Judicial Watch, a conservative campaign group frequently praised by Trump online.

Those perceived to be standing in Trump’s way were attacked. The Russian operation allegedly shared an article attacking Mueller published by the rightwing website World Net Daily and used critical talking points that have also been used by Republican allies of the president.

Operatives were also directed to share articles published by the rightwing sites True Pundit, Breitbart and Fox News attacking the late Senator John McCain, House speaker, Paul Ryan, Senate majority leader, Mitch McConnell, and Senator Marco Rubio for being insufficiently supportive of Trump’s agenda.

Members of the Russian operation also posed as Americans to create bogus profiles on Facebook under names such as “Helen Christopherson”, “Bertha Malone” and “Rachell Edison”, according to prosecutors. These accounts then contacted real Americans to promote political events, share racist content or show support for groups such as the National Rifle Association (NRA).

Late in 2017, the Russians also used the Twitter account @CovfefeNationUS – the name referring to a notorious typing error in a tweet by Donald Trump – to post or repost more than 23,00 messages. They had previously created other pro-Trump accounts including @UsaUsaforTrump, @TrumpWithUSA and @swampdrainer659.

Russians working for the operation were directed to create “political intensity” by supporting “radical groups” and “users dissatisfied with the social and economic situation” in the US, according to prosecutors. One of the Russians said they sought to “aggravate the conflict between minorities and the rest of the population”.

They created bogus social media profiles purporting to be African Americans railing against the Trump administration, black voting rights and the debate over NFL players kneeling during the national anthem.

Having pushed criticism of Mueller, the Russians allegedly later used Twitter accounts to retweet messages endorsing his investigation and to stoke anger among his supporters, urging people to “take to the streets in protest” if Trump fired the special counsel.

The prosecution of Khusyaynova is being handled by the US attorney’s office in Alexandria, Virginia, rather than by Mueller.