US Secretary of State Hillary Clinton has defended her handling of the attack on the US mission in the Libyan city of Benghazi, during a US Senate hearing.

Mrs Clinton told lawmakers that she took responsibility for the incident in which US Ambassador Christopher Stevens and three other Americans were killed, but also defended herself.

She interrupted one senator to contradict him and stressed that she did not see requests for additional security to protect the Benghazi mission.

Mrs Clinton cast the incident as part of a long history of such violence as well as the result of regional instability since the Arab Spring of popular revolutions began in 2011.

Senator Bob Corker, a senior Republican, kept up the criticism of the Obama administration, saying the Benghazi attack and the US response displayed "woeful unpreparedness" for the events sweeping the region.

Speaking in congressional testimony delayed by more than a month because of her ill health, Mrs Clinton's spoke of comforting families who lost loved ones in the attack, the first since 1988 in which a US ambassador was killed.

"For me, this is not just a matter of policy - it's personal," Mrs Clinton told the Senate Foreign Relations Committee on what is likely to be the last day that she will testify before Congress before stepping down as secretary of state.

"I stood next to President (Barack) Obama as the Marines carried those flag-draped caskets off the plane at Andrews," she added, describing the ceremony at Andrews Air Force Base when the men's remains were brought home.

"I put my arms around the mothers and fathers, the sisters and brothers, the sons and daughters and the wives left alone to raise their children," she said.

The attack could haunt Mrs Clinton should she decide to run again for president in 2016, a possibility she has played down.

Militants attacked and overwhelmed the US diplomatic facility in the Libyan city on 11 September, 2012 in a sustained assault.

The official inquiry concluded that the State Department was completely unprepared to deal with the attack, citing "leadership and management" deficiencies, poor coordination and unclear lines of authority in Washington.

The inquiry did not find Mrs Clinton personally at fault.

"I take responsibility," Mrs Clinton said, echoing comments she first made in a TV interview on 15 October and stressing that she has accepted all of the recommendations of an independent review panel that ultimately held lower-level officials responsible.

"Nobody is more committed to getting this right. I am determined to leave the State Department and our country safer, stronger and more secure," she added.

Four State Department officials were put on administrative leave following the board's report.

A separate Senate committee report said the State Department made a "grievous mistake" in keeping the Benghazi mission open despite inadequate security and increasingly alarming threat assessments in the weeks before the attack.

Mrs Clinton is due to testify later in the day before a House of Representatives committee.

The controversy over the Benghazi attack also cost Susan Rice, the US ambassador to the United Nations, her chance to succeed Mrs Clinton as secretary of state.

Republicans in Congress harshly criticised Ms Rice for her comments days after the attack in which she said the incident appeared to be the result of a spontaneous demonstration rather than a planned assault.