Abdel Hafiz Ghoga, deputy chairman of the ruling National Transitional Council (NTC), told a news conference in the eastern city of Benghazi that an investigation had already been launched, and "whoever is responsible for that [Qaddafi's killing] will be judged and given a fair trial."
Until now, the NTC had claimed that Qaddafi was killed in a crossfire after he was captured in his hometown of Sirte.
The 15-member UN Security Council, meanwhile, decided to terminate on October 31 the NATO campaign in Libya. The mandate was approved in March after Qaddafi unleashed deadly reprisals on protesters.
Reports say that Qaddafi's former intelligence chief, Abdullah al-Senussi, has crossed from into Mali from Niger, and that Qaddafi's son, Saif al-Islam, is also on his way to Mali.
Both Senussi and Saif are wanted by the International Criminal Court (ICC) in The Hague for crimes against humanity.
NTC officials said on October 26 that Saif was trying to negotiate his surrender to the ICC.
compiled from agency reports