The International Criminal Court chief prosecutor has said there are serious suspicions that the killing of Libyan leader Moamer Kadhafi was a war crime.
Luis Moreno Ocampo also said the Libyan government must tell the court by January 10 whether they will hand over Kadhafi's son Seif al-Islam.
Kadhafi was captured and killed on October 23 in murky circumstances, and Moreno-Ocampo told reporters Thursday "we are raising our concerns" with the interim government and asking how it would investigate crimes by all sides in the uprising against the Libyan strongman.
"The death of Moamer Kadhafi is one of the issues to be clarified -- what happened -- because there are serious suspicions that it was a war crime," Moreno Ocampo told reporters after briefing the UN Security Council.
A UN commission of inquiry is also to go to Libya and Moreno-Ocampo said he would speak with member nations of the Security Council to see if they had evidence on the Kadhafi killing.
The prosecutor said his investigators were in Libya last week to pursue the inquiry. "We are working very closely to the government of Libya which has to manage a very complex situation," he said.
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There has been international unease over the way Kadhafi died after opposition fighters dragged him out of a concrete sewage pipe where he had been hiding near his home city of Sirte.
Videos taken at the time showed him alive. Subsequent footage shows a bloodied Kadhafi being hustled through a frenzied crowd, before he disappears in the crush and the crackle of gunfire can be heard.
Kadhafi's son was captured last month and ICC judges will have to decide on any challenge by the Libyan government to their authority to try the case. Libya has said it wants a national trial for Seif.
Moreno-Ocampo told AFP in an interview that the government will not have to transfer Seif to the tribunal in The Hague before any decision is taken.
"The judges are asking the Libyan government if they are going to surrender Seif. In a letter sent to the judges, they said they would first investigate all the crimes in Libya," Moreno-Ocampo said.
"So we will see what the government says. They have been asked to reply before January 10," he added.