|Opposition protesters in the country's east have set up advanced positions to guard against pro-Gaddafi forces [AFP]
At least 1,000 people protesting against the rule of Muammar Gaddafi have taken to the streets of Tripoli, the Libyan capital, raising fears of fresh conflict between anti-government protesters and loyalist forces.
Protests called by the opposition began on Friday when worshippers streamed out of a mosque in the centre of the city, chanting "Gaddaf is the enemy of God", witnesses said.
"This is the end for Gaddafi. It's over. Forty years of crimes are over," Faragha, an engineer at the protest, told the Reuters news agency.
Pro-Gaddafi forces fired tear gas at protesters, with the AP news agency reporting that at least five cannisters were fired at the crowd in the district of Tajoura in the capital.
"They fired teargas. I heard shooting. People are scattering," a reporter from the Reuters news agency in Tajoura said.
Anita McNaught, Al Jazeera's correspondent in Tripoli, said that there was a heavy security presence in the city.
"There is some evidence that there's been burning tyres, but beyond that it has been essentially a state of lockdown," she said.
"The shops are shut, the streets are empty, minimal traffic and an extremely high and visible security presence in all major intersections in the city."
Government forces set up checkpoints in Tripoli ahead of the action, and residents said soldiers had been roaming the city in civilians cars.
Some news agencies have also reported a crackdown on foreign journalists, saying security guards have attempted to block their movements.
Internet services have also reportedly been disrupted in Tripoli and the eastern city of Benghazi.
Meanwhile, Interpol, the international police agency, has issued an international "Orange Notice" alert for Gaddafi and 15 members of his inner circle to help police around the world enforce UN sanctions aimed at Libya.
"The individuals subject to the Orange Notice have been identified as being involved in or complicit in planning attacks, including aerial bombardments, on civilian populations," Interpol said.
Vowing "victory or death", eastern-based rebels pressed home a westwards push towards Gaddafi's Tripoli stronghold with an attack on the oil town of Ras Lanuf, which lies on a strategic coastal road, claiming to have taken its airport.
In the west, security forces loyal to Gaddafi launched an offensive to retake Az Zawiyah, a town near the capital that has
for days been defying his rule.
Residents said 30 civilians had been killed in the fighting and there were reports that the town's rebel commander was among the dead.
Al Jazeera and agencies