TRIPOLI, Libya — Libya’s interim leader said today he has ordered an investigation into Moammar Gadhafi’s death in response to strong international pressure to determine how the ousted leader was killed by a bullet to the head shortly after he was captured alive.

Mustafa Abdul-Jalil told a news conference in the eastern city of Benghazi that the National Transitional Council has formed a committee to investigate Thursday’s killing amid conflicting reports of how the dictator who ruled Libya for 42 years died.

Government officials have said initial findings suggest Gadhafi was killed in the crossfire as his supporters clashed with revolutionary forces seizing control of his hometown of Sirte.

But Abdul-Jalil raised a new possibility today, suggesting that Gadhafi could have been killed by his own supporters to prevent him from implicating them in past misdeeds under his regime.

“Let us question who has the interest in the fact that Gadhafi will not be tried. Libyans want to try him for what he did to them, with executions, imprisonment and corruption,” he said.

“Free Libyans wanted to keep Gadhafi in prison and humiliate him as long as possible. Those who wanted him killed were those who were loyal to him or had played a role under him, his death was in their benefit.”

The U.S., Britain and international rights groups have called for an investigation into whether Libya’s former rebels killed a wounded Gadhafi after pulling him out of a drainage pipe.