The Pentagon says the U.S. Air Force has carried out its first drone missile strike in Libya on Saturday, though it's providing no details.

Libyan government officials confirmed that NATO carried out another series of air strikes on Tripoli early Saturday.

Reporters were taken to an unpaved plot next to Libyan dictator Moammar Gadhafi's sprawling Bab Aziziyeh residential compound.

They were shown two craters, apparently from missiles that had pierced through thick layers of reinforced concrete, laying bare what looked like a bunker system.

Eight narrow military-issue metal crates were stacked next to one of the craters.

It was unclear what military equipment the crates contained.

Loud booms were heard in the city early on Saturday, apparently from airstrikes. There were no immediate reports of casualties.

NATO stepped into the Libyan fighting in mid-March, unleashing airstrikes against Libyan military targets as part of a UN mandate to protect Libyan civilians.

Reports that two missiles struck the compound came shortly after the Libyan government said it was ready to withdraw from Misrata, 190 kilometres east of Tripoli. And it appears, that is what has happened.

Ghadafi forces flee Misrata

Government troops retreated to the outskirts of Misrata under rebel fire Saturday and the opposition claimed victory following nearly two months of fighting in the third-largest city.

A rebel spokesman said soldiers had booby trapped bodies and buildings as they fled. Reports on Saturday say the hospital is still under the control of Gadhafi's forces.

However, most of the city of 300,000 people was calm with rebel forces taking over several key buildings that had been filled with government soldiers, including snipers. An eight-story insurance building — pockmarked by shells and scorched around the windows — had been used by snipers because it was the tallest in central Misrata and commanded a view of the city.

The only fighting Saturday was on the eastern outskirts of the city, where about 150 pro-Gadhafi soldiers trying to withdraw were fighting rebels said the spokesman, adding that ambulances were picking up dead and injured.

Deputy Foreign Minister Khaled Kaim sought to portray the move as a decision by tribal leaders to give the army an ultimatum to step aside if it cannot retake control of Misrata. The tribal leaders would fight the rebels, Kaim said late Friday night.