Libya's new leadership will formally proclaim the country's liberation Sunday after the death of Muammar Qadhafi, while NATO has tentatively decided to end its mission over the country on 31 October.
But some observers suggested the deposed dictator may have been summarily executed after his capture Thursday. Russia, the UN's human rights chief, Amnesty International and Qadhafi's widow all called for a probe.
The US said the National Transitional Council should provide a "transparent account" of Qadhafi's death.
"The announcement of the liberation will be announced in Benghazi at 5:00 pm (1500 GMT) on Sunday, at the court of justice," said a senior NTC official, speaking on condition of anonymity.
Benghazi, Libya's second city, is where rebels first rose up against the Qadhafi's regime in February, and where the National Transitional Council (NTC), the country's new regime, is still based.
With the death of Qadhafi, his son Muatassim and other top regime figures, and the fall of his hometown Sirte, the promised declaration was widely expected.
It will be followed by the formation of an interim government to oversee drawing up a new constitution and free elections after four decades of dictatorship.
But with another Qadhafi son – longtime heir-apparent Seif al-Islam – still unaccounted for, NTC leaders have waited, despite jubilation in towns across the country at the news that the once all-powerful tyrant was dead.
On Friday, Qadhafi's body was being held in a refrigerated chamber outside Misrata, an AFP correspondent reported, with the authorities wanting to run DNA tests before the burial.
NTC leaders were vague about the actual burial, not wishing to see the grave become a rallying point for residual loyalists.
Questions remain over how Qadhafi met his end after NTC fighters hauled him out of a culvert where he was hiding. Several videos show him still alive at that point.
Footage showed the former dictator, his face half-covered in blood, being dragged towards a vehicle by a delirious crowd and forced onto the bonnet.
Those at the front pushed and shook him, pulled him by the hair and hit him. At one point he appeared to be trying to speak.
Subsequent footage showed him being hauled off the vehicle, still alive, and hustled through the screaming crowd, before he disappears in the crush and the crackle of gunfire can be heard.
NTC leaders are adamant he was shot in the head when he was caught "in crossfire" between his supporters and new regime fighters soon after his capture.
"There have been rumours flying around since the killing of Qadhafi, after images were released, claiming that our revolutionaries slaughtered him," a senior NTC official said.
"No instructions were given to kill Qadhafi, and we do not believe our revolutionaries intentionally killed him."
But in a video circulating on the Internet, a young fighter from Benghazi claims he shot Qadhafi twice after capturing him: once under the arm and once in the head. He says he died a half hour later.
Calling for a probe Russian Foreign Minister Sergei Lavrov said "images we saw on television show that he was taken prisoner while wounded, and then later, once already a prisoner, his life was taken away."
US State Department spokesman Mark Toner said the NTC "has already been working to determine the precise cause and circumstances of Qadhafi's death, and we obviously urge them to do so in an open and transparent manner as we move forward."
UN human rights chief Navi Pillay also called for an investigation.
"On the issue of Qadhafi's death yesterday, the circumstances are still unclear," her spokesman Rupert Colville said. "There should be some kind of investigation given what we saw yesterday."
Claudio Cordone, senior director at Amnesty International, said that if Qadhafi "was killed after his capture, it would constitute a war crime and those responsible should be brought to justice."
Paris and Washington revealed that their aircraft had intervened when a convoy, believed to be carrying Qadhafi, fled Sirte as NTC fighters overran the last redoubt of loyalist forces.
French Defence Minister Gerard Longuet said Libyan fighters then stepped in, destroying the vehicles, from which "they took out Colonel Qadhafi."
The air strikes marked the culmination of a NATO-led air war, which was operating on the strength of a UN mandate to protect civilians from Qadhafi's forces.
Gathered in Brussels on Friday, NATO ambassadors decided to end the seven-month air and sea mission in Libya on 31 October, NATO chief Anders Fogh Rasmussen said.
"We agreed that our operations are very close to completion and we have taken a preliminary decision to end Operation Unified Protector on 31 October," Rasmussen said.
"In the meantime, I will consult closely with the United Nations and the National Transitional Council," he added.
"I'm very proud of what we have achieved, together with our partners, including many from the region."
NATO would continue to "monitor the situation and retain the capacity to respond to threats to civilians, if needed," Rasmussen added.
Russia on Friday demanded the UN Security Council immediately end the no-fly zone.
Russia presented a draft resolution to the other 14 members of the council aiming to end the sanction, the country's UN envoy Vitaly Churkin told reporters.
