WASHINGTON (AP) -- Former Trump campaign chairman Paul Manafort and his business associate, Rick Gates, have been indicted by a federal grand jury on charges of conspiracy against the United States and other felony charges.

The indictments unsealed Monday in Washington contain 12 counts, including conspiracy to launder money, failing to register as a foreign agent, false statements, and multiple counts of failing to file reports for foreign bank accounts.

The charges are the first in special counsel Robert Mueller's investigation into potential coordination between Russia and the Trump campaign. Details on the charges have not been released.

Mueller was appointed as special counsel in May to lead the Justice Department's investigation into whether the Kremlin worked with associates of the Trump campaign to tip the 2016 presidential election.

Manafort, of Alexandria, Va., and Gates, of Richmond, Va., turned themselves in to the FBI on Monday morning.

The White House had no comment.

Meantime, the top Democrat in the House is pressing for an "outside, fully independent investigation" to expose Russia's meddling in the election and the involvement of Trump officials.

In a statement Monday shortly after indictments were unsealed,  Minority Leader Nancy Pelosi of California said that even with the accelerating special counsel probe and congressional investigations, another inquiry was warranted.

Pelosi said that defending the integrity of the country's democracy "demands that Congress look forward to counter Russian aggression and prevent future meddling with our elections."