The Trump administration placed new sanctions on a Russian tycoon who the Treasury Department said is a prime financier of a troll farm that used social media to influence the 2018 midterm elections.

The Treasury Department’s sanctions on Yevgeniy Prigozhin and six employees of the ­infamous Internet Research Agency targeted his assets, including three private planes and a yacht used by his family for vacations.

The Treasury Department said the newest sanctions are the first made under an executive order President Trump signed a year ago as a warning to countries interfering in U.S. elections. But it underscored concerns about foreign influence in the 2020 elections.

“Free and fair elections are the cornerstone of American democracy, and we will use our authorities against anyone seeking to undermine our processes and subversively influence voters,” said Treasury Secretary Steven Mnuchin in a statement. “The administration will work tirelessly to safeguard our electoral process and will aggressively pursue any other foreign actor that attempts to interfere in the 2020 elections.”

The United States previously has imposed sanctions on Prigozhin, though he has denied having any involvement in the Internet Research Agency. Prigozhin is a close ally of Russian President Vladi­mir Putin.

The Internet Research Agency was indicted by special counsel Robert S. Mueller III on charges of interfering in the 2016 election. The company, which is based in St. Petersburg, employs Russians who have posed as Americans on social media pages and websites and who posted extremist messages on racial issues, sexual identity and guns that have fomented division in U.S. politics.

Earlier this year, the U.S. Cyber Command shut down Internet access at the firm’s St. Petersburg facility in the hours before the 2018 midterms and for a few days afterward, sources told The Washington Post.

In a statement on the Russian version of Facebook, Prigozhin said at the time, “I cannot comment on the work of the Internet Research Agency in any way because I have no relation to it.”

The Treasury Department said the Internet Research Agency deployed numerous ruses in the 2018 midterms to undermine the vote. They included a staged video and a statement on a website called the Internet Research Agency American Division discrediting candidates considered hostile to Russia.

The Treasury Department said the Internet Research Agency attempted to influence the 2018 midterms through videos and by posting extremist views, but said there “was no indication that foreign actors were able to compromise election infrastructure that would have prevented voting, changed vote counts, or disrupted the tallying of votes.”

Photos of one of Prigozhin’s private jets and his yacht, the St. Vitamin, were culled from social media sites and presented by the Treasury Department. It said the planes are owned by front companies controlled by Prigozhin. They are registered in Seychelles, the Cayman Islands and the Isle of Man, the Treasury Department said, and they have logged numerous flights throughout Africa, the Middle East and Europe.

The Treasury Department said anyone doing business with Prigozhin or using one of his planes or yacht could face secondary sanctions.