It was unclear who was doing the shooting, which started at 5:45 am (0345 GMT), just before daybreak, or what had caused it. Machine gun volleys, some of them heavy calibre, were reverberating around central Tripoli, along with ambulance sirens, pro-Qaddafi chants, whistling and a cacophony of car horns as vehicles sped through the vicinity.
A government spokesman denied any fighting was under way in Tripoli. "I assure you, I assure you, I assure you, I assure you, there is no fighting going on in Tripoli," said Mussa Ibrahim, a government spokesman.
"Everything is safe. Tripoli is 100 percent under control. What you are hearing is celebratory fireworks. People are in the streets, dancing in the square." He warned, however: "I would like to advise not to go there for your safety.
The armed revolt was inspired by generally peaceful uprisings that toppled despots in neighbouring Egypt and Tunisia and have spread to other Arab countries with long entrenched leaders and a deficit of democracy, good governance and jobs.
Libyan rebels were also advancing from the east on Qaddafi's hometown Sirte, around 500 km (300 miles) from Tripoli, and clinging to positions in a western town near the capital after withstanding two armoured assaults by government forces.
A tense calm settled over the western town of Zawiyah after nightfall on Saturday, with rifle-toting insurgents on rooftops and manning checkpoints on streets leading into the centre.
But the rebels said they were bracing for another tank and artillery attack by government on Sunday.
A doctor in Zawiyah, some 50 km (30 miles) west of Tripoli, said at least 30 people, mostly civilians, were killed during fighting on Saturday that wrecked the town centre, raising to at least 60 the death toll from two days of battles.
Almost 600 km (400 miles) to the east along Libya's Mediterranean coast, insurgents said they took the town of Bin Jawad on Saturday, on the heels of seizing the oil port of Ras Lanuf, and were thrusting westwards towards Sirte.
Exultant after asserting control over much of the east of the vast oil-exporting North African state in a revolt against the flamboyant autocrat Qaddafi, some rebels said an assault on Sirte was imminent.
"We're going to attack Sirte, now," rebel fighter Mohamed Salim told Reuters, while another fighter, Mohamed Fathi, said: "Listen, we have no organisation and no military plan. We go where we're needed."
"If (rebels) can expand down into the Gulf of Sirte ... they've got a very good shot at independence at the least – or maybe even overturning him at the most," said Peter Zeihan, analyst with the US-based Stratfor intelligence newsletter.
But others were wary of the limitations of an undisciplined rebel force made up of soldiers who have bolted from Qaddafi's ranks and volunteers who have more enthusiasm than experience.
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