At least seven loud blasts were heard in Tripoli early on Friday morning as bombs fell in the vicinity of Muammar Gaddafi's main compound of Bab al-Aziziya.
An Associated Press correspondent staying in a hotel in the capital said he heard the explosions and saw flames in the air as bombs struck the ground. Nato jets were heard circling the sky above.
Residents in Tripoli also told The Associated Press that at least three blasts were 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 Gaddafi's sprawling Bab al-Aziziya compound, which is the Libyan leader's main headquarters and acts as a military barracks.
Just 48 kilometers to the west of the capital, opposition fighters in Libya's western mountains claimed control yesterday of the country's last functioning oil refinery, a blow to Muammar Gaddafi's regime in a week of stunning rebel advances that could turn the tide of the 6-month-old civil war.
The refinery is located in the strategic city of Zawiya, where rebels have made great strides in battles with government forces since their initial assault on Saturday.
A rebel victory in Zawiya could leave Gaddafi nearly cornered in his increasingly isolated stronghold of Tripoli, the capital, just 50 kilometers to the east along the Mediterranean coast.
Rebel fighters are now closing in on the capital from the west and the south, while Nato controls the seas to the north.