The death of Abdel Fatah Younis was announced at a press conference in the rebel capital, Benghazi, by the head of the rebels' National Transitional Council, Mustafa Abdul Jalil. He told reporters that rebel security had arrested the head of the group behind the killing.

Rebel security had earlier summoned Younis for questioning about suspicions his family still had ties to Muammar Gaddafi's regime.

Younis was Gaddafi's interior minister before defecting to the rebels early in the uprising.

Abdul Jalil said Younis had been summoned for questioning regarding "a military matter". He said Younis and his two aides were shot before they arrived for questioning.

Abdul Jalil called Younis "one of the heroes of the 17th of February revolution", a name marking the date of early protests against Gaddafi's regime.

While he criticised Gaddafi for seeking to break the unity of rebel forces, he did not say directly that Younis's killers were associated with the regime. Instead, he issued a stiff warning about "armed groups" in rebel-held cities, saying they needed to join the fight against Gaddafi or risk being arrested by security forces.