President Trump's former campaign manager Paul Manafort on Monday afternoon pleaded not guilty to all charges from special counsel Robert Mueller, who is conducting an investigation into ties between the Trump campaign and Russia.

Manafort's former business associate Richard Gates also pleaded not guilty.

Judge Deborah Robinson agreed to federal prosecutors' request to set bail at the notably high amount of $10 million. Unsecured bail was set at $5 million.

Prosecutors have also requested that Manafort be released on house arrest in Virginia. The special counsel's office considers him a flight risk, lawyers in Mueller's office argued before Robinson on Monday afternoon, citing the seriousness of the charges and the extent of Manafort's ties abroad.

The bureau took possession of Manafort's passport yesterday, his lawyer said.

Manafort surrendered himself to FBI agents on Monday morning after being charged with 12 counts, including conspiracy against the U.S. The indictment also included Gates, a protégé of Manafort's who was ousted from the pro-Trump group Americas First Policies earlier this year.

A sprawling 31-page indictment, unsealed on Monday morning, lays out the charges, which are related to work Manafort and Gates did on behalf of a Kremlin-backed political party in Ukraine. Mueller alleges the two men were paid tens of millions of dollars that they then laundered "in order to hide Ukraine payments from United States authorities."

Manafort is accused in the indictment of using the laundered money to buy luxury goods in the U.S..

The indictment makes no mention of Manafort's work for Trump's campaign, which began in March of 2016 and ended with his ouster in August.

Speculation has roiled that Mueller may be attempting to push Manafort to cooperate with the broader Russia probe - to "flip" on bigger fish.

A separate indictment was also unsealed on Monday, revealing that a former Trump campaign aide, 30-year-old George Papadopoulos, had pleaded guilty last month to lying to investigators in the Mueller probe. The indictment accuses him of lying about conversations he had with a foreign professor who told him he had thousands of emails containing "dirt" on Democratic candidate Hillary Clinton.

The indictment also accuses Papadopoulos of lying about his contact with a female Russian national, whom the man mistakenly thought was a relative of Russian President Vladimir Putin, in an effort to arrange a meeting between the Trump campaign and Russian officials.

It is unclear whether Papadopoulos is now cooperating with Mueller's investigation. The announcement of his plea was released an hour or so after news broke about Manafort and Gates.