WASHINGTON (REUTERS) - The Republican National Committee (RNC) filed two lawsuits on Wednesday seeking to obtain emails related to Democratic presidential candidate Hillary Clinton's tenure as the United States' secretary of state.

Clinton, front-runner to be her party's candidate in November's general election, has faced questions about her emails since it emerged a year ago that she used a private email account and a private server during her time in the post from 2009 to 2013.

Clinton has apologised for the email arrangement, which is being investigated by the Federal Bureau of Investigation, but has said she did nothing wrong and believes the government will vindicate her.

The RNC said it filed the lawsuits after the State Department failed to respond in a timely manner to a Freedom of Information Act request submitted in December. It sought the information to ensure the public has information to decide if Clinton is "fit to serve" as president, the RNC said in a statement.

The first lawsuit seeks emails, BlackBerry Messenger or text messages between then-Secretary of State Clinton and several key senior aides, including her chief of staff, Cheryl Mills, and director of policy planning, Jake Sullivan.

The second lawsuit seeks emails and other electronic exchanges between nearly a dozen State Department officials and any Clinton associate using one of more than a dozen different Internet domain names. It covers the period between Feb 1, 2013, when Clinton left the job, and Dec 4, 2015.

The request includes any emails to the State Department officials from Clinton's campaign website, HillaryClinton.com, or the website of former President Bill Clinton's foundation, ClintonFoundation.org.

The suit also targets emails from domains like MediaMatters.org, a liberal non-profit group that seeks to counter what it believes is misleading conservative information in the US media.