WASHINGTON (Reuters) - U.S. prosecutors have accused Russian operatives of seeking to interfere with a federal agency charged with policing American elections, as part of their case relating to interference in the 2016 U.S. presidential contest, saying the group aimed to interfere with a ban on some election spending by foreign nationals.

In a court document released on Tuesday, federal prosecutors said they would ask a U.S. grand jury to issue a superseding indictment, alleging the Russia-based Internet Research Agency conspired “to interfere with more than one lawful function of the Federal Election Commission.”

The prosecutors would not seek to add charges or expand the conspiracy, they wrote in the filing submitted to the U.S. District Court for the District of Columbia as part of the case, which is among those that have stemmed from U.S. Special Counsel Robert Mueller’s investigation into Russian interference in the 2016 U.S. election.

“The defendants not only conspired to interfere with the enforcement of the disclosure requirements set forth in the Federal Election Campaign Act, but that they also conspired to interfere with the related FEC function of enforcing the statutory ban on certain expenditures by foreign nationals,” prosecutors wrote in the filing.

The FEC is an independent and bipartisan government agency charged with enforcing campaign finance law for federal elections. However, three of the FEC’s six seats are vacant.

Representatives for the agency said the FEC could not comment on pending litigation. Representatives for the Internet Research Agency could not be immediately reached.

Mueller secured an indictment against 13 Russian individuals and three firms, including the Russian government propaganda arm Internet Research Agency based in St. Petersburg, and accused them of tampering in the 2016 U.S. presidential race to support Donald Trump and disparage his then-rival, Democrat Hillary Clinton.

Members of the Russian group have also been targeted by U.S. sanctions.

Social media accounts linked to the network have been targeted by Facebook and Twitter ahead of the 2020 U.S. elections and upcoming contests elsewhere.

U.S. Senate investigators also found that Russian propaganda efforts have increased since Trump’s 2016 election victory.

The U.S. prosecutors said they would present their request to the federal grand jury at a hearing scheduled for Nov. 15.