A former trusted deputy of Colonel Mummar Gaddafi is reported to have left Tripoli and joined the rebels in another blow to the Libyan regime's efforts to cling to power.
Abdel Salam Jalloud, who helped Gaddafi seize power in 1969 and was prime minister between 1972 and 1977, was reported to have left the capital city and travelled with his family to the Zintan region of the country in the Western Mountains.
Since the 1990s Jalloud has been under near-house arrest, having retired from politics. However he is a former close ally of Gaddafi, and his decision will likely be a boost for the rebels.
The opposition television channel Libya Awalam quoted Jalloud as saying that "Gaddafi's regime is finished".
There were also reports that other top figures from the regime had defected, including Omran Abukraa, Libya's oil chief. He is now in Tunisia, having decided not to return to Tripoli following a trip overseas.
Earlier in the week a senior security figure in the regime also escaped the country and flew to Tunisia with his family.
The defections come as Libyan opposition forces reported fresh gains of territory close to the capital.
The rebels said they had captured the industrial section of the port city of Brega, which contains one of the country's largest oil refineries.
The residential areas of the city had been captured last week, but rebel spokesperson Colonel Ahmed Bani said that the whole city had now been "liberated".
"All of it is under our control," Col Bani told reporters on Saturday. "The fighters are in the port and have taken the refineries."
Two rebels were killed in the fighting and fifteen were injured, another spokesperson said.
Battles also continued to rage in the coastal city of Zawiya, which is just 30km from Tripoli.
Fighting continued through Friday and into Saturday over the centre of the town, but that too now appears to be under rebel control.
A TV station in Qatar broadcast a statement which called for residents of Tripoli loyal to Gaddafi to prepare for the arrival of the rebels.
"Tripoli is the largest of our cities," the statement said. "Do not leave it to the scum. The rebels are coming."