US presidenctial candidate Hillary Clinton on Thursday said she took responsibility after an attack on a US consulate in Libya in 2012 left four Americans, including the ambassador, dead.She told a Congressional committee that as secretary of state she introduced reforms to protect diplomatic staff after the attack, CNN reported.Committee chairman Trey Gowdy said: "We owe them (the victims) the truth."Clinton's Democratic Party says the Republican-led panel was a witch-hunt trying to harm her presidential bid.In her opening statement, she said she had asked Chris Stevens, one of the four killed, to go to Libya as US envoy."After the attacks I stood next to President (Barack) Obama as Marines carried his casket," she said."I took responsibility, and as part of that before I left office I launched reforms to better protect our people in the field and help reduce the chance of another tragedy happening in the future."