The Federal Bureau of Investigation (FBI) is looking into newly discovered emails linked to Hillary Clinton’s just 11 days before the presidential election, reigniting a massive controversy that has haunted the Clinton campaign for months.

Three months after the investigation into Ms Clinton's emails recommended no criminal charges be filed, FBI director James Comey said on Friday he had found more messages that appeared to be "pertinent" to the investigation of Ms Clinton’s alleged misuse of her personal email server when she was Secretary of State.

The emails on a government computer were reportedly obtained via the FBI's investigation into former congressman Anthony Weiner, the former husband of Clinton aide Huma Abedin, over allegations he sent sexual messages to a minor.

Speaking about the investigation on Friday evening, Ms Clinton said she had learned of the newly discovered emails from news reports.

Ms Clinton said that “the American people deserve to get the full and complete facts immediately. She urged the FBI to ”explain this issue in question, whatever it is, without any delay.“

“Let's get it out,” she added.

Republicans have seized on the news to denounce her candidacy, while Clinton campaign chair John Podesta said the FBI "owes the American public" the full details of what it has found to clear up any whiff of controversy so soon before the election.

“I'm confident whatever they are will not change the conclusion reached in July,” Ms Clinton said.

In a statement earlier in the day, Mr Comey said: “In previous congressional testimony I refer to the fact that the FBI has completed its investigation of former secretary Clinton’s personal email server.

"Due to recent developments I am writing to supplement my previous testimony.

"In connection with an unrelated case the FBI has learned of the existence of emails that appear to be pertinent, and I am writing to inform you that the investigative team briefed me on this yesterday and I agreed the FBI should take appropriate investigative steps designed to allow investigators to review these emails to determine whether they contain classified information, as well as to assess their importance to our investigation."

He said he "cannot yet assess whether or not this material may be significant", and did not say how long the investigation would take.

Few details are available. The emails were found on a government computer and were not related to WikiLeaks.

FBI director says 'no charges' for Hillary Clinton amid email scandal

The email controversy has dogged Ms Clinton's campaign for months.

She repeatedly said she handed over 33,000 emails to the FBI and the Justice Department to determine whether she had sent or received top secret or classified information on an unsecured server.

The FBI also denied a "quid pro quo" arrangement with the state department to downgrade certain information in the emails from "classified" to "unclassified".

Trump Blasts Clinton Over Leaked DNC Emails

Mr Comey told the Justice Department in July that although Ms Clinton had displayed "extreme carelessness" which could have lead to adversaries hacking her account, he did not recommend any criminal charges.

The Justice Department agreed with the FBI's recommendation the same month.

As the news broke, Ms Clinton was flying to Iowa to speak alongside women's rights leaders at two rallies. Ms Clinton did not comment on the news during her first rally Friday afternoon at Cedar Rapids.

At a rally in New Hampshire, Donald Trump told the crowds: "Hillary Clinton’s corruption is on a scale we have never seen before. We must not let take her criminal scheme into the oval office.

"I have great respect for the fact that the FBI and the Department of Justice are now willing to have the courage to right the horrible mistake that they made."

He has previously said Ms Clinton should be behind bars and accused her of "deleting thousands of emails" to hide them from the FBI, which Ms Clinton denied.

The news was also jumped on by Republicans including house speaker Paul Ryan, who said Ms Clinton had "nobody but herself to blame but herself".

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"She was entrusted with our nation's most important secrets, and she betrayed that trust by carelessly mishandling highly classified information," he said in a statement, renewing his call to exclude Ms Clinton from any classified briefings until the matter was "fully resolved".

Republican National Committee chairman Reince Priebus also called for Ms Clinton to be "disqualified" from running for president.

Donald Trump's campaign manager Kellyanne Conway said on Twitter that a "great day" for their campaign "just got even better".