Libya conflict: Heavy gunfire erupts in Tripoli
Explosions and sustained gunfire have been heard in parts of Tripoli, as rebels close in on the Libyan capital.
A BBC correspondent in the city says it sounded like exchange of fire rather than celebratory gunshots.
Residents spoke of clashes in the city, amid reports that opponents of Col Muammar Gaddafi were being urged to go on the streets.
The rebels earlier claimed control of of Zlitan, 160km (100 miles) east of Tripoli, and Zawiya, 30km to the west.
However, pro-Gaddafi forces have been fighting back at the oil port of Brega, with the rebels admitting that they fell back from the eastern town's industrial zone under heavy bombardment.
Gaining momentum
There are reports of protests and gunfire in areas to the north and east, including the Tajoura district, where there was trouble at the start of this uprising against Col Gaddafi, the BBC's Matthew Price in Tripoli reports.
One credible source told the BBC there was heavy fighting in the city.
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We will be victorious”
Moussa Ibrahim Col Gaddafi's Information Minister
Col Gaddafi's Information Minister Moussa Ibrahim said late on Saturday that the situation was under control, putting the trouble down to "small armed gangs".
"We will be victorious," Mr Ibrahim said.
Col Gaddafi certainly has support in Tripoli, our correspondent says.
In recent weeks at night more and more checkpoints have sprung up across the city. Pro-Gaddafi men and women have received weapons training.
However, rebel TV said this was the start of the uprising in the capital.
The momentum is clearly against Col Gaddafi and his supporters, our correspondent adds, with rebels having better weaponry.
Heavy shelling
A rebel military spokesman, Col Ahmed Bani, earlier confirmed that rebel forces had fallen back in Brega.
Brega, home to Libya's second-largest hydrocarbon complex and the place where the country's main oil fields feed into for refining, has repeatedly changed hands during the six-month-old conflict.
"Yesterday, the industrial zone was under our complete control, but the truth is that today the situation has changed due to heavy artillery shelling," Col Bani said on Saturday.
"We withdrew to the eastern part of the industrial zone."
After visiting Zlitan, the BBC's Orla Guerin said the rebels appeared to have a firm grip on the town, controlling the centre and manning checkpoints.
However, small-arms and mortar fire could still be heard, and rebels told the BBC that beyond a strategic bridge in the centre, there was still a risk of attack.
The BBC's Rupert Wingfield-Hayes in Zawiya said the rebels have succeeded in pushing Col Gaddafi's forces out of the city.
He said the bodies of sub-Saharan Africans could be seen on the streets, amid claims by the rebels that many of those fighting for Col Gaddafi were foreign mercenaries.
Rebel forces have also moved towards Tripoli from the south.
The BBC's Rupert Wingfield-Hayes in Zawiya says pro-Gaddafi forces no longer control the area
Nato, enforcing a UN-mandated no-fly zone to protect civilians since March, controls sea access to Tripoli.
Late on Friday, Col Gaddafi's Information Minister, Moussa Ibrahim, continued to insist government troops had the upper hand in both Zlitan and Zawiya.
Workers stranded
Meanwhile, reports suggest fresh senior figures in the Gaddafi camp may have defected:
Abdel Salam Jalloud, who helped Col Gaddafi come to power in 1969 but fell out with him in the 1990s, is believed to be making his way to Europe from neighbouring Tunisia
Libyan Oil Minister Omran Abukraa failed to return to Libya on Thursday after a visit to Italy and went to Tunisia instead, Tunisian sources said
Libya's conflict broke out in February, inspired by uprisings in Tunisia and Egypt which toppled the presidents of those countries.
Rebels in the east rapidly consolidated their gains, but a stalemate developed in the west as rebels there faced overwhelming military force.
The fighting has stranded thousands of migrant workers - many of them Egyptians - in Tripoli.
The International Organisation for Migration (IOM) said it was planning to evacuate them in the coming days.
Since the conflict in Libya began, an estimated 600,000 migrant workers have fled the country, many with the help of the IOM, but many remain.