Libya's ruling National Transitional Council said Thursday it will prosecute the killers of ousted Libyan leader Moammar Gadhafi, if an investigation shows he died after his capture.

NTC leaders have been under intense pressure to investigate the circumstances of Gadhafi's death last week after initially saying he was killed in crossfire after being pulled from a drainage pipe.

Video has raised the possibility he was shot and killed as provisional government forces stormed his hometown of Sirte. Witnesses have offered conflicting information as to how Gadhafi died.

Libya's Deputy U.N. Ambassador Ibrahim Dabbashi said Wednesday initial reports show no transitional fighters shot at Gadhafi after he was arrested. Dabbashi told the U.N. Security Council the ousted leader was bleeding from his abdomen and head when he was arrested, and that he died after arriving at a hospital in Misrata.

In other news, a lawyer representing former Libyan prime minister Al-Baghdadi Ali al-Mahmoudi said he has been freed by a Tunisian court.

Mahmoudi fled to Tunisia after Gadhafi's regime collapsed in August, and was recently arrested while trying to cross into Algeria. He went on a hunger strike to protest his possible extradition to Libya.

In New York, the U.N. Security Council adopted a resolution Thursday that would end authorization of NATO's mission in Libya, despite calls from Libyan officials for the mission to be extended.

Last week, NATO announced preliminary plans to phase out its six-month-old air campaign on October 31. But Libya's interim leaders, citing security concerns, have urged NATO to continue its mission until at least the end of the year.

NATO operations in Libya were launched under a Security Council resolution to protect civilians from attacks by Gadhafi's military during the conflict.