WASHINGTON, June 15 (Xinhua) -- A U.S. federal judge on Friday revoked former Trump campaign chairman Paul Manafort's bail and ordered him to jail pending trial, citing newly filed obstruction of justice charges.

The judge made the decision after special counsel Robert Mueller, who's leading the investigation into Russia's role in the 2016 U.S. presidential election, alleged that Manafort and one of his associates had tried to tamper with witnesses in the case.

According to reports, two witnesses reported to Mueller that Manafort had attempted to influence their testimony.

Prosecutors argued on Friday that Manafort could continue to engage in alleged criminal activity if he is not jailed.

Manafort entered a not guilty plea to charges for witness tampering and conspiracy to obstruct justice.

Manafort is the first Trump campaign official to be jailed as part of Mueller's investigation. He was first indicted last fall and has remained on home confinement.

His trial in Alexandria, the U.S. state of Virginia, on bank fraud charges is set in July, and a separate one in Washington, D.C., for him on charges of money laundering and fraud conspiracy is scheduled for September.

He has also pleaded not guilty to those charges.

Manafort will remain in jail while awaiting those trials in coming months. It's not clear when he could be taken into custody and where he could be held.

Trump has sought to distance his campaign and himself from Manafort. Speaking to reporters at the White House on Friday, Trump insisted that Manafort only worked on the campaign "for a very short period of time."