David Petraeus, the former CIA director, told congressional hearings on Friday that he had always known a terrorist group had been involved in an attack in Benghazi that left the US ambassador and three other Americans dead.

According to reports from members of Congress who attended the closed-door hearings, Petraeus said the information had been included in the original set of talking points prepared by the CIA for the Obama administration. But he said it was removed from the one provided to the UN ambassador, Susan Rice, who used it as the basis for a series of interviews on the weekend after the killings.

Rice is among the contenders to replace Hillary Clinton as US secretary of state. In a press conference this week, Barack Obama, angrily criticised two Republican senators, John McCain and Lindsey Graham, who threatened to block her nomination if the president put her name forward.

Petraeus, who gave evidence to both the Senate and House intelligence committees, said that references to the group alleged to have been behind the 11 September attack were in the CIA’s classified talking points, which were classified, but removed from the unclassified memo relied upon by Rice. The reason, he said, was not to tip off the group about what the US authorities knew.