The center of Tripoli was blanketed with smoke and fireballs.
Moussa Ibrahim, a Libyan government spokesman, told CNN at least three people were killed and 150 others were wounded.
On Monday, forces loyal to Gadhafi attacked a rebel-held border crossing into Tunisia in a battle that resulted in nine deaths, a rebel military commander said.
The NATO strikes were aimed at a guard compound for pro-Gadhafi military volunteers that had been emptied in anticipation of an attack, Ibrahim said.
A statement issued by NATO said the attack targeted a "regime storage facility" adjacent to the Bab-al-Azizia compound using precision-guided weapons.
The facility resupplies Libyan government forces that NATO said have been attacking civilians.
The strikes, which took place during the early morning hours, woke up residents living more than a mile away from the targets, The New York Times reported.
"We thought it was the day of judgment," a Tripoli resident told the Times.
The strikes were almost continuous for about a half-hour, the Times reported.
It was one of the heaviest attacks against Tripoli since the NATO mission began just over two months ago, CNN reported.
The raid suggested NATO is trying to break what has become a stalemate in Libya, observers said.
There were other signs of such a development Monday, including a visit by Jeffrey Feltman, the senior Middle East official in the U.S. State Department, to the de facto rebel capital of Benghazi.
French Defense Minister Gerard Longuet announced Britain and France plan to add helicopter gunships to their forces involved in the Libyan air war.