James Comey, director of the US Federal Bureau of Investigation (FBI), told American lawmakers on Sunday that newly discovered emails concerning an investigation into Democratic presidential candidate Hillary Clinton's use of a private email server during her tenure as state secretary do not warrant charges.

Clinton's Communications director Jennifer Palmieri told reporters: "We're glad this matter is resolved." At Clinton's Ohio rally with basketball superstar LeBron James, however, the issue went unmentioned. 

US Republican Jason Chaffetz, who has led a Congressional investigation into the case, said that Comey informed him and other lawmakers of federal investigators' conclusions.

Last month, Comey informed members of Congress that the bureau discovered new emails that warranted a review of his conclusion's in July.

The emails were discovered during a separate investigation of former Congressman Anthony Weiner, the estranged husband of top Clinton aide Huma Abedin, sources close to the investigation told American newspaper "The New York Times."

'Always confident'

Comey was strongly criticized by officials, the White House and Clinton's campaign for not providing further information when he notified Congress of the new emails.

Officials in the US Justice Department said the move is inconsistent with department policy which directs against actions which could be viewed as affecting the election or helping a candidate, an official said.

Clinton campaign spokesman Brian Fallon said he welcomed the FBI's latest conclusion concerning the emails.

"We were always confident nothing would cause the July decision to be revisited. Now Director Comey has confirmed it," Fallon said.

Following the news on Sunday, however, Republican presidential candidate Donald Trump accused the FBI of impropriety. At a rally in the Detroit suburbs, Trump said it would have been impossible for the FBI to review what has been reported to be as many as 650,000 emails in such short a time.

"Hillary Clinton is guilty. She knows it, The FBI knows it. The people know it," Trump said, insisting that the former secretary of state was being protected by "a rigged system."

The US is set to vote for the next US president on Tuesday, November 8.

ls,ksb/rc, jm (AP, Reuters)