Libya's transitional rulers were optimistic Thursday that their forces would soon seize Sirte, the hometown of fugitive leader Moamer Gaddafi, dpa reported.
"The city will be under our full control in four days' time," said Abdel Salam Mansour, a rebel commander fighting in Sirte.
"The revolutionaries are in a good position on all fronts of Sirte," he was quoted as saying, by Libyan online newspaper the New Qureena.
Forces loyal to Libya's transitional rulers have been fighting for three weeks to control Sirte on the Mediterranean coast, where diehard Gaddafi loyalists are showing fierce resistance.
The capture of the city will be a major boost to the morale of the North African country's new rulers, who have delayed announcing a new government until all of Libya is "liberated."
"The (pro-Gaddafi) snipers positioned on rooftops inside Sirte have been using civilians as human shields since the revolutionaries entered the city," said Mansour.
Thousands of civilians have fled Sirte amid warnings from human relief organizations that people caught in the crossfire are facing a severe shortage of medical and food supplies.
In Brussels, United States Defence Secretary Leon Panetta said Thursday that NATO's decision to end its campaign in Libya hinged on four conditions.
First, NATO was waiting for the outcome of the battle over Sirte, which remains a stronghold of forces loyal to Gadaffi, Panetta said.
Second, the Western alliance wanted to make sure that pro-Gaddafi forces were no longer able to attack civilians.
Panetta listed two further conditions - that Gaddafi no longer exercises control over his loyalists and that rebel forces are able to "provide security" over the entire country.
"The decision ... will depend a great deal on the recommendation of our commanders ... but ultimately it is a decision of ... all the political leaders that are involved," Panetta said after a two-day meeting of NATO defence ministers.
NATO's top commander in Europe, US Admiral James Stavridis, added that Panetta's conditions were "not a series of precise metrics," but rather gave "a sense of the situation" that the alliance was looking for before ending its six-month war effort.
Meanwhile, two mass graves containing around 900 bodies were reportedly found in the Libyan capital Tripoli.
"Statements from witnesses led us to two graves of victims of the former regime," broadcaster Al Jazeera quoted Nagui al-Essawi, a military commander in Tripoli, as saying.
He added that the two graves had been discovered in Gargaresh, a coastal area located some 7 kilometres from central Tripoli, and in Brasta Milad, a rural area near the capital.
Al-Essawi, however, did not give dates for when the victims were believed to have been killed.
In September, rebel officials announced the discovery of a mass grave containing the remains of around 1,200 people near the notorious Bu Salim Prison in Tripoli, where a massacre took place in 1996.
The ruling Transitional National Council has accused the Gaddafi regime of killing thousands during an armed conflict that started in February.