Explosions were reported as bombs struck the ground, with Nato jets heard circling above.
Residents in Tripoli also reported at least three blasts heard on the road leading to the airport in the capital.
Nato has been bombarding military targets in Libya since a no-fly zone was instituted in March. That includes areas near and in Col Gaddafi’s sprawling Bab al-Aziziya compound, the Libyan leader’s main headquarters which also acts as a military barracks.
Rebel fighters were closing in on the capital from the west and the south, while Nato controls the seas to the north. The opposition is in control of most of the eastern half of the country and has declared Benghazi, 620 miles east of Tripoli, as its de facto capital.
Families fleeing their homes to avoid a possible rebel assault on Tripoli described growing tensions and deteriorating living conditions in the capital.
Security forces have blanketed the city with checkpoints, gun battles are heard after nightfall and power cuts last days. Just 30 miles to the west, opposition fighters in Libya’s western mountains claimed control of the country’s last functioning oil refinery, in Zawiya, on Thursday, a blow to Col Gaddafi’s regime in a week of rebel advances that could turn the tide of the six-month-old civil war.
A rebel victory in Zawiya could leave Col Gaddafi nearly cornered in his increasingly isolated stronghold.
Nato planes targeted a small boat carrying Col Gaddafi’s troops off the coast at Zawiya yesterday.
A spokesman said it was struck because the troops were “threatening civilians” and said its planes also destroyed five tanks in the city.
In the UK, the Prime Minister underlined his “optimism” for Libya’s democratic future as he welcomed to Downing Street the newly appointed charge d’affaires to Britain.
David Cameron greeted Mahmud Nacua as he arrived for a meeting at Number 10 alongside seven representatives from the Libyan community in the UK.
Last month the Foreign Office invited the National Transitional Council (NTC) to take over the Libyan embassy in London and representatives moved in last week.
Britain has officially recognised the rebel-backed NTC as Libya’s legitimate government after kicking out supporters of Col Gaddafi’s regime. Opening the meeting yesterday, Mr Cameron said he had earlier had a “very positive” phone conversation with NTC chairman Mustafa Abdul Jalil.