"Let this serve as a warning," the US Secretary said in a statement

The United States on Monday slapped fresh sanctions on a businessman tied to Russian President Vladimir Putin as well as to a disinformation operation accused of conspiring to manipulate the 2018 midterm elections.

The financial sanctions, which target Russian financier Evgeny Prigozhin, some luxury assets and members of the so-called Internet Research Agency, are the first the US Treasury has taken under an executive order on election interference signed last year President Donald Trump.

"Let this serve as a warning," US Secretary of State Mike Pompeo said in a statement following the Treasury's announcement.

Those who fail to distance themselves from the sanctions' targets, or who provide landing rights and service Prigozhin's targeted aircraft and yacht, may also be subject to future sanctions, Pompeo said.

The Treasury's action follows a Washington Post report on Friday that Trump had told senior visiting Russian officials in 2017 he was not concerned by Russian efforts to sway the 2016 election in his favor.

The sanctions announced Monday marked the third time the US had added Prigozhin's name to its list of foreign nationals formally barred from the US financial system, a move which freezes him out of much of the global financial system as well.

US prosecutors last year indicted the Internet Research Agency as well as alleged employees, charging them with a broad conspiracy to influence the 2016 elections by spreading disinformation in the United States via social media and stolen identities.

The Treasury said Monday the IRA had last year announced its intention to do likewise in the 2018 midterms by seeking to discredit candidates it viewed as hostile to Moscow.

But there was no evidence they prevented voting, altered vote counts or disrupted vote tallying, the Treasury said.

Treasury announced it was also designating six IRA members for acting to interfere in the 2018 elections.

Treasury also announced it was placing sanctions on three aircraft and a yacht belonging to Prigozhin and three entities incorporated in the Seychelles which he used to manage these properties.