US presidential candidate Hillary Clinton has apologised for using a private email server in her New York home for her work as secretary of state.

In an interview yesterday, she said: "That was a mistake. I'm sorry about that. I take responsibility."

The front-runner for the Democratic Party's nomination in the 2016 presidential election made the comments in an interview with ABC News.

In two earlier interviews in the past week, Ms Clinton had declined to apologise for the controversial email arrangement while working as the nation's top diplomat, saying it was allowed by the State Department.

She has been forced to defend herself against growing scrutiny by journalists and political opponents of how she handled sensitive government information since the email arrangement first came to light in March.

The Federal Bureau of Investigation is now examining the server to see whether any information, including classified information, was mishandled.

Initially, Ms Clinton said she handled no classified information on her unsecured private email server, a practice which the government forbids.

More recently, she has said she sent and received no information that was "marked" that way.