TRIPOLI, Libya - NATO air strikes rattled the Libyan capital Thursday as clusters of bombing runs appeared to target the outskirts of Tripoli.

At first, the intensity of the attacks suggested a return to the heavy NATO bombardment that hit military installations across the capital Tuesday and flattened buildings in Moammar Gadhafi's sprawling compound in the center of the city.

By nightfall Thursday, there were 14 air attacks, far fewer than on Tuesday. There were eight explosions in a first series of strikes Thursday, and hours later, the sound of six more air strikes boomed in the distance. Government officials did not say what was hit in the bombing runs.

The strikes are in support of a four-month-old uprising that seeks to push Gadhafi from power after four decades. Rebels have taken control of swaths of eastern Libya, although fighting has since become a stalemate even with NATO support.

Gadhafi shows no signs of ceding power under the building pressure of the NATO strikes, despite repeated attacks on his compound, government buildings, military radar emplacements, and other army installations.

But CIA chief Leon E. Panetta said in testimony before the Senate on Thursday that the NATO military operation, strong economic sanctions, and enforcement of a no-fly zone were putting tremendous pressure on Gadhafi.

President Obama has named Panetta to take over as defense secretary.

Among other signs of building pressure, Secretary of State Hillary Rodham Clinton said Thursday that there were "numerous and continuing" overtures by people close to Gadhafi to negotiate his departure.

Speaking to reporters after an international conference on Libya in the United Arab Emirates, Clinton said proposals from "people close to Gadhafi" included the "potential for a transition."

On Wednesday, Gadhafi forces renewed shelling near the port city of Misrata, killing 10 rebel fighters. Misrata is one of the few footholds rebels have in western Libya.

NATO said it destroyed an "electronic warfare vehicle" and military training camp in the vicinity of the city as government forces renewed their assault on the city.

In Brussels, Belgium, on Thursday, NATO Secretary-General Anders Fogh Rasmussen said the shelling near Misrata underscored the continued need to protect civilians.

"It is an example that the Gadhafi regime still constitutes a threat to the civilian population," he said.

News media in neighboring Tunisia reported more defections Thursday from Gadhafi's military, including a general and 10 ranking officers who they said crossed this week.