Hillary Clinton campaign
Clinton is expected to run as a candidate in the 2016 presidential race Reuters

Hillary Clinton has urged US officials to release the e-mails she allegedly sent from a private account during her tenure as secretary of state, after the messages were subpoenaed.

This follows a State Department probe into Clinton's use of a private account — hdr22@clintonemail.com — to conduct government business.

State Department officials believe Clinton's use of a private account may have breached US federal law, which dictates that e-mails from public officials must be classed as government records.

Clinton's emails were subpoenaed on Wednesday (4 March) by a Republican-led congressional committee investigating the attack on the US embassy in Benghazi in 2012, in which US Ambassador Christopher Stevens was killed.

The subpoenas from the Select Committee on Benghazi demanded additional material from Clinton and others related to Libya, spokesman Jamal Ware said. The panel also instructed technology companies it did not identify to preserve any relevant documents in their possession.

Clinton has already had to hand over 55,000 pages of emails to the State Department.

As secretary of state from 2009 to 2013, Clinton did not have a government email address, the US state department told The New York Times. Associated Press also revealed Clinton had her own internet server at her home in New York.

Clinton emailed so frequently using her BlackBerry as secretary of state that it became an Internet meme.

Tweet to release emails

In a tweet this morning (5 March), Clinton, who is widely believed to be planning a bid for the Democratic presidential nomination in 2016, tweeted: "I asked State to release them [emails]. They said they will review them for release as soon as possible."

In response, a State Department spokeswoman indicated it would review the emails provided by Clinton "as soon as possible", but that, given the sheer volume of her correspondence, it would take a while.

Clinton's tweeted statement came just hours after a Republican-led congressional committee demanded that the former secretary of state turn over all emails relating to the Benghazi attack, in which four Americans died.

"It doesn't matter if the server was in Foggy Bottom, Chappaqua or Bora Bora," House Speaker John Boehner said. "The Benghazi Select Committee needs to see all of these emails, because the American people deserve all of the facts."

The chairman of the Benghazi committee, Trey Gowdy, told reporters: "I want the documents. Sooner rather than later."

But Democrats on the committee have criticised the decision, calling it a fishing expedition.

"Everything I've seen so far has led me to believe that this an effort to go after Hillary Clinton, period," Elijah Cummings, a top Democrat on the committee, said in a statement.

Cummings highlighted the fact that Colin Powell, secretary of state of former president George W Bush, had also used his personal email address.