Rebel fighters celebrate after taking control of the coastal town of Sabratha (Reuters photo)
The rebels, who have transformed the battlefield this week with victories taking them ever closer to the city, launched an assault east of the capital but were taking heavy casualties, a Reuters reporter at the front line said.
Rebel advances west and south of Tripoli in recent days have cut the road links between the capital and the outside world and severed the supply lines of Gaddafi's forces, putting his 41-year-old rule under unprecedented pressure.
In a sign of fighting hitting closer to Gaddafi's inner circle, the brother of the spokesman who has served as the leader's public face was reported killed.
A Reuters reporter said rebels had launched an assault on Gaddafi's forces in Zlitan, east of the capital, where fighting has been bloodier and advances far slower than in the west. A large number of wounded were being brought to the rebels' field hospital.
The rebels suffered a setback on Thursday when Gaddafi's forces crushed an uprising inside Zlitan.
A spokeswoman for the International Organization for Migration (IOM), Jemini Pandya, said an operation to evacuate thousands of Egyptians and other foreigners trapped in Tripoli by the latest fighting would begin within days.
"We are looking at all options available, but it will probably have to be by sea," she told a Geneva news conference.
More than 600,000 of an estimated 1.5 million to 2.5 million foreigners, most of whom are Asian and African migrant workers, have fled six months of fighting in Libya. However, many have remained in Tripoli, which until this week was far from fighting and a safe two-hour drive from the Tunisian border.
Moussa Ibrahim, the spokesman whose briefings and interviews have been broadcast worldwide throughout the six-month-old uprising, has served as the highest-profile face of Gaddafi's government.
His brother, a 25-year-old student named Hasan Ali, was killed by a NATO helicopter gunship in the central square of Zawiyah after going there with a group of others to check on friends, a Libyan official said.
"We are surprised by this and we condemn it. NATO planes have become a way of killing civilians and providing air cover for rebels to advance on Libyan cities," he said.
Zawiyah, west of the capital, fell to the rebels his week, transforming the long-stalemated conflict by blocking the road linking Tripoli to the Tunisian border.
Ibrahim, who has repeatedly denied reports of rebel advances, said on state television on Thursday: "We reassure people that we are making progress on all fronts." According to the JANA news agency, he promised all Libyans payments of 500 dinars, about $300, as reward for being steadfast.
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