Voters will choose a 200-member assembly which will elect a prime minister and cabinet before laying the ground for full parliamentary elections next year under a new constitution.
Candidates with Islamic agendas dominate the field of more than 3,700 hopefuls, suggesting Libya will be the next "Arab Spring" country after Egypt and Tunisia to see religious parties secure footholds in power after last year's uprisings.
But the credibility of the vote will be wrecked if armed militia with regional or tribal loyalties discourage voters from turning out, or if disputes over the outcome degenerate into pitched battles between rival factions.
"The election will go ahead tomorrow and all the Libyan people need for it to go ahead," Prime Minister Abdurrahim El-Keib told a news conference in the capital Tripoli on Friday.
The greatest threat comes from the eastern region around the city of Benghazi, cradle of the NATO-backed uprising that ousted Gaddafi nearly a year ago but which complains of neglect by the interim government in Tripoli in the west.
"There is no doubt there could be a civil war between us in the east and the west," Hamed al-Hassi, a former rebel who now heads the High Military Council of Cyrenaica, the name of the eastern region, told Reuters.
"The country will be in a state of paralysis because no one in the government is listening to us," said Hassi, whose group is charged with securing the east but has fallen out with the government over representation.
On Friday, local armed groups shut off half the North African country's oil exports to press their demands for greater representation in the new national assembly. At least three major oil exporting terminals were affected.
"The strikes will continue for 48 hours if the government does not respond positively to their requests," said a note to oil companies from shipping agents.
"NO SECURITY"
Hundreds of demonstrators gathered in a square in central Benghazi late on Friday, saying they would boycott the vote in protest at the fact that the east had been allotted only 60 seats in the assembly compared to 102 f o r the west.
In the latest attack on election authorities in the east, a helicopter carrying voting material had to make an emergency landing near Benghazi on Friday after being struck by anti-aircraft fire. One person on board was killed.
"There is no security in this country," Emad El-Sayih, deputy head of the High National Election Commission, told Reuters.
Concerns exist elsewhere. In the isolated southern area of Kufra in the Saharan desert, tribal clashes are so fierce that election observers will be unable to visit, and some question whether the vote can proceed in certain areas there.
In Gaddafi's hometown of Sirte, a former fishing village on the southern rim of the Mediterranean Sea, the mood ahead of the polls was restrained, with some saying they would not vote.
"They should take care of us first, look at our homes," said Abed Mohammed, a resident of District Two neighbourhood which saw some of the heaviest fighting and where Gaddafi was believed to have hidden before being captured and killed.
"We are not against elections in the future, but first things first," he said.
Yet many Libyans are eager for a first taste of democracy and will be heading enthusiastically to the polls.
While analysts say it is hard to predict the political make-up of the new assembly, parties and candidates professing an attachment to Islamic values dominate and very few are running on an exclusively secular ticket.
The Justice and Construction offshoot of Libya's Muslim Brotherhood is tipped to do well, as is al-Watan, the party of former CIA detainee and Islamist insurgent Abdel Hakim Belhadj.
Parity rules for the new assembly mean there are many female candidates. Yet many of their campaign posters in Tripoli have been defaced, underlining the ambivalence felt by some in Libyan society about a greater female role in politics.
"Politics is a new field for men and women in Libya," said Lamia Busidra, 38, a leading candidate for the al-Wattan party in Benghazi. "The qualifications are there, women can do it, they just need the confidence in themselves to do it."
Early partial results after polls close at 8pm (local time) on Saturday will give some guide to the make-up of the assembly but full preliminary results are not due until Monday.
