Clinton takes aim at FBI chief over decision to reopen email probe

US Democratic presidential candidate Hillary Clinton on Saturday accused the head of the Federal Bureau of Investigation (FBI), James Comey, of "deeply troubling" behaviour a day after the bureau reopened a probe into her emails.

Renewed investigations by the FBI into Clinton's emails related to her use of a private server as secretary of state have taken centre stage just ten days before the elections, with her rival, Republican candidate Donald Trump, trying to seize the opportunity to portray her as unfit to lead the country.

Speaking to volunteers in Daytona Beach, Florida, Clinton said, "Some of you may have heard about a letter the FBI director sent" on Friday to the US Congress stating that the agency is again reviewing her emails.

"It is pretty strange to put something like that out with such little information right before an election," Clinton said, adding, "It's not just strange, it's unprecedented and it's deeply troubling because voters deserve to get full and complete facts."

She urged Comey to "put it all out on the table."

Comey had announced in July that the FBI was not going to seek Clinton's prosecution after the initial investigation showed she had used several email servers and devices while in office, receiving content which was later classified as sensitive.

Fellow Democrats on Saturday also worked to pressure Comey to provide an explanation for the reopening of the probe.

Four US senators – Patrick Leahy, the longest-serving Senate Democrat; Dianne Feinstein; Thomas Carper; and Benjamin Cardin – wrote to Comey and US Attorney General Loretta Lynch to ask they provide more detailed information about investigative steps underway by Monday.

Clinton's campaign team tried to downplay the new review.

"There's no evidence of wrongdoing, no charge of wrongdoing," said John Podesta, who heads the Clinton campaign.

Trump seizes opportunity

Trump leapt on Comey's statements, devoting a large part of a campaign speech in Golden, Colorado, to attacking Clinton and arguing that she is not to be trusted with the presidency.

"Her criminal action was willful, deliberate, intentional and purposeful," Trump said.

"Hillary set up an illegal server for the obvious purpose of shielding her illegal actions from public disclosure and exposure."

Trump also charged that the US Justice Department, led by appointees of Democratic President Barack Obama, is trying to help Clinton.

"The attorney general didn't want anything to happen to Hillary. I wonder why. It's very sad. Folks, we're living in a third world country," he said.

"Hillary Clinton's corruption is corrosive to the soul of our nation and it must be stopped."

Clinton herself has repeatedly attacked Trump as not fit to be president.