The State Department on Friday released a first batch of emails by Hillary Clinton, giving an unprecedented glimpse into the work of the former top diplomat in the wake of a deadly 2012 attack on a US mission in Libya.

The emails have stoked fresh controversy since Clinton -- who is now running for president -- admitted to using a private server and email address during her tenure as secretary of state from 2009 to 2013.

She has also come under fire from Republicans for the Department's handling of a militant attack on the US mission in Benghazi in eastern Libya on September 11, 2012 amid allegations of a cover-up over what really happened.

Both issues are likely to stalk Clinton as she bids to become the first woman to occupy the Oval Office in the 2016 elections, hoping to slide into the seat once held by her husband, former president Bill Clinton.

A total of 296 emails -- out of a trove of 30,000 -- sent or received by Clinton were released Friday and uploaded onto a State Department website, which promptly crashed under the weight of traffic.

Some of the emails were long memos from a long-time Clinton family friend and advisor, Sidney Blumenthal, using information from "sensitive sources" with access to Libyan officials.

Initially, Blumenthal said that then Libyan president Mohammed Megaryef had been told the attacks were "inspired by what many devout Libyans viewed as a sacrilegious Internet video."

But only hours later on September 12, he sent another long email marked "just in" from his mobile phone.

"Libyan security officials believe that the attack was carried out by forces of the Islamist militia group calling itself the Ansar al-Sharia brigade; working out of camps in the eastern suburbs of Benghazi," it stated.

Clinton forwarded the email from her account to trusted foreign policy advisor Jake Sullivan, saying: "We should get this around asap." Sullivan replied: "Will do."

- Condolences -

There were also messages of condolences from senior State Department staff at the deaths of the four Americans, and tributes to Clinton for her speech at Andrews Air Force base when the bodies were brought home.
"Your remarks this afternoon at Andrews were wonderful," wrote then deputy secretary Bill Burns on September 14. "Thanks for doing so much for our institution on such a sad day."

Clinton and her staff also closely monitored an appearance by national security advisor Susan Rice when she took to the Sunday morning talk shows on September 16 to discuss the attack.

"She wasn't asked whether we had any intel. But she did make clear our view that this started spontaneously and then evolved," Sullivan wrote to Clinton.

"The only troubling sentence relates to the investigation specifically," he added, after Rice told ABC television's "This Week" that the administration would have to wait and see if things "might have unfolded differently in different circumstances."

Many of the other emails appear to be press articles being forwarded to Clinton by her chief of staff Cheryl Mills and other aides.

- Emails 'don't change the facts' -

"The emails we release today do not change the essential facts or our understanding of the events before, during, or after the attacks," State Department deputy spokeswoman Marie Harf insisted.

The emails span two years from January 1, 2011 when the political upheavals in Libya began to December 31, 2012. And many of them have been heavily redacted after being deemed to hold classified information.
Clinton has said she used her own server and email address for "convenience" and has turned over about 30,000 emails, amounting to some 55,000 pages, to the State Department.

"No one has a bigger interest in getting them released than I do," she said earlier this week.

Paper copies of the emails sent on two private addresses (hdr22@clintonemail.com and hrod17@clintonemail.com) were handed over in December in 12 large boxes labelled with a rough time stamp for the documents inside.

A State Department team has been busy digitizing them and plowing through the emails since March to black out any classified or sensitive information.

Clinton said she had handed over every email relevant to her job as America's top diplomat and destroyed all the rest, which she maintained were personal.