 Libyan rebels launched an assault early Sunday on the capital of Tripoli amid unconfirmed reports that leader Moammar Gadhafi had fled, NBC News reported. Fighting was still raging around Mitiga airbase in Tripoli's Tajourah district after midnight, an opposition activist told a Reuters journalist outside Libya. Earlier on Saturday evening, residents told Reuters of gunfire and street protests in several parts of Tripoli. “If you can call any mobile number in Tripoli, you will hear in the background the beautiful sound of the bullets of freedom.” 
 
 Phone calls to several Tripoli residents from different neighborhoods confirmed widespread gunfire and explosions. White House officials said President Barack Obama, vacationing at Martha's Vineyard, Mass., "had been briefed on Libya and is getting regular updates as needed." The six-month-old war came close to the Tunisian frontier after rebels suddenly seized the coastal city of Zawiyah just 50 km (30 miles) west of Tripoli, surrounding the heavily fortified capital and severing its vital supply routes. Intense fighting continued in Zawiyah, home to an important oil refinery, on Saturday and rebels occupying the center of the city said pro-Gaddafi forces showed no sign of retreat. East of Tripoli, fighting has been bloodier and rebel advances far slower. NATO BOMBINGS 
 
 NATO warplanes have hammered Gaddafi military targets since March under a U.N. mandate to protect civilians. In another potential blow to Gaddafi, a Tunisian source said Libya's top oil official, Omran Abukraa, had arrived in Tunisia after deciding not to return to Tripoli from a trip to Italy. If confirmed, his defection would be the third of a senior government official in the past week. A senior security official arrived in Rome on Monday, and rebels said on Friday that Gaddafi's estranged former deputy Abdel Salam Jalloud had joined their side in the western mountains. A second senior official said the administration was in close contact with the Libyan opposition and U.S. allies and partners, and believes that Gadhafi's days in power are numbered. Mustafa Abdel-Jalil, the chairman of the rebel government, the National Transitional Council, said that he hoped Colonel Qaddafi and the rest of his inner circle would follow.
– It looks like Libyan rebels are closing in for the kill: Reuters reports heavy gunfire and explosions in Tripoli. Rebels have made swift progress this week knocking off strategic cities around the capital, and now it, too, looks in danger of falling. Residents tell the news agency that people are in the streets in some areas shouting anti-Gadhafi slogans. A government spokesman, however, took to state television to downplay the unrest: "All of Tripoli is safe and stable." Even if that's true, it probably won't be for long, a US assistant secretary of state tells the New York Times. “It is clear that the situation is moving against Gadhafi," says Jeffrey D. Feltman. "The opposition continues to make substantial gains on the ground while his forces grow weaker.” Already, rumors are circulating that Gadhafi himself has fled Tripoli, reports NBC News, but there's no confirmation. Earlier reports had him poised to leave for Tunisia.