Clashes broke out in several towns in Libya after the opposition called for a day of protests while supporters of Libyan leader Muammar Gaddafi rallied in the capital.
A resident in the eastern city of Benghazi said at least five people had been killed in violence in nearby towns, but with phone lines out of order and access barred for journalists, it was impossible to establish an exact death toll.
Opponents of Gaddafi, communicating anonymously online or working in exile, had urged people to protest to try to emulate the popular uprisings which unseated long-serving rulers in neighbouring Tunisia and Egypt.
In the capital Tripoli, there was no sign of unrest, according to a Reuters reporter said, apart from the pro-Gaddafi demonstrators in the city's Green Square chanting ‘We are defending Gaddafi!’ and waving his portrait.
There were also reports of several deaths in Ajdabiya, about 160km west of Benghazi.
The towns are all part of the same eastern Cyrenaica region centred on Benghazi where the worst clashes appear to have taken place and where support for Gaddafi has historically been weaker than in other parts of the country.
Quryna newspaper, which is based in Benghazi, reported that the regional security chief had been removed from his post over the deaths of protesters in Al Bayda.
New York-based Human Rights Watch said Libyan authorities had detained 14 activists and writers who had been preparing the anti-government protests.
In a possible move to calm the unrest, Quryna, which has ties to Gaddafi's son Saif al-Islam, reported Libya's parliament was preparing to adopt ‘major shifts’, including government personnel changes.
Political analysts say an Egyptian-style revolt is unlikely because the government can use oil revenues to smooth over most social problems.
Libya has been tightly controlled for more than 40 years by Gaddafi.