Libyan security forces are using tear gas to disperse hundreds of protesters from the streets after Friday prayers in Muammar Gaddafi's stronghold of Tripoli.
The opposition had called for demonstrations against the Libyan leader following the prayers.
A BBC reporter in the flashpoint eastern suburb of Tajoura says demonstrators were burning the official Libyan flag.
The reporter says protesters have taken to the streets and are calling for the fall of the Gaddafi government.
A Reuters news agency reporter says 14 pick-up trucks, apparently carrying pro-Gaddafi forces, have been seen speeding into the area.
Protests in Tripoli last week after Friday prayers ended in bloodshed when government forces fired on civilians, according to witnesses.
Fresh air attacks in east
In the east of the country, Libyan rebels have come under attack by a warplane for a third day as Colonel Gaddafi tries to loosen the opposition's expanding grip on a key coast road near the town of Ajdabiyah.
Rebels guarding a military base there say a Libyan warplane bombed just beyond the walls of the base but did not hit it.
The Al Arabiya news network is reporting that Colonel Gaddafi's forces have also renewed their bombing of the oil terminal town of Brega.
The rebels have been preparing to repel attacks by forces loyal to Colonel Gaddafi, as both sides struggle for control of the strategic coastal road and oil industry facilities.
Reports say several hundred members of the Tuareg community from Mali have gone to Libya to join forces loyal to Colonel Gaddafi.
Eastern-based rebels spearheading the two-week-old revolt say they are open to talks only on Colonel Gaddafi's exile or resignation following attacks on civilians.
The attacks have brought global condemnation and triggered a probe at the war crimes court.