U.S. Secretary of State Hillary Clinton
U.S. Secretary of State Hillary Clinton Reuters

Democratic presidential candidate Hillary Clinton denied on Saturday that she used a private email account to send or receive classified information while she was secretary of state.

"I did not send nor receive anything that was classified at the time," Clinton said at a campaign stop in Iowa, according to the Reuters news agency.

The comments came after it was revealed that an internal government review had found that Clinton sent at least four emails from her personal account containing classified information during her time heading the State Department.

In a letter to members of Congress on Thursday, the inspector general of the intelligence community, Charles McCullough concluded that Clinton’s email contains material from the intelligence community that should have been considered “secret” at the time it was sent.

Clinton said on Saturday she had "no idea" what were the emails mentioned in the letter.

McCullough's letter said a sampling of 40 of about 30,000 emails sent or received by Clinton found at least four that contained information the government had classified as secret.

The information was classified at the time that the emails were sent, McCullough said.

Clinton is facing criticism for having used a personal email address during her entire four years as secretary of state, despite the fact that under specific guidelines signed into law by President Barack Obama, government email accounts are supposed to be used in any situation involving official business.

Clinton has said she used private emails out of "convenience", though she has also admitted it "would have been better" to have two accounts to separate work and personal emails.

Republicans have accused Clinton of trying to avoid disclosure laws through her use of private systems.

Clinton, considered a front-runner for the Democratic presidential nomination, said on Friday in New York that there were “inaccuracies” in reports about her email usage, but didn’t offer specifics, according to the report.

She noted that she has voluntarily released 55,000 pages of email and offered to testify before a congressional committee. Last month, the State Department said it cannot find 15 work-related emails from Clinton's private server that were released by a committee probe of the 2012 Benghazi attacks.