By Marie-Louise Gumuchian and Hadeel Al Shalchi
TRIPOLI (Reuters) - Libyans will vote in their first free national poll in more than half a century on Saturday amid fears that violence could taint an election meant to usher in an interim national assembly and draw a line under Muammar Gaddafi's 42-year autocratic reign.
Voters will select a 200-member assembly that will choose a Cabinet to replace the self-appointed interim government. The new chamber will also pick a new prime minister and help draft a constitution aimed at turning Libya into a unified, stable state. Many of the 3,700 candidates have strong Islamic agendas.
The election will be closely watched around the world by both supporters and critics of NATO's bombing campaign that helped underpin an "Arab Spring" uprising which ended Gaddafi's dictatorship and finally claimed his life.
Yet for many of the 2.7 million registered voters, excitement about a first taste of democracy is mingled with fear that it will be hijacked by the militias, often with regional loyalties, who have flourished amid prevailing lawlessness.
"This is a new beginning for us, we are learning democracy," said Tarek Mabrouk, a shop keeper in Tripoli. "We all hope that it will go well so we can move forward."
Once the country's new constitution is drafted, a referendum will be held and, if it establishes a parliamentary system, a full legislative poll will be held within six months.
While the election is designed to produce a government with a stronger mandate to rule than the current ex-rebel National Transitional Council (NTC), the credibility of the result will be questionable if voters are too scared to turn out or if post-vote disputes degenerate into gun battles among rival factions.
In some areas, such as the isolated southern district 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.
Less than a year after rebel fighters overran the capital Tripoli with little resistance, Libya is a country enjoying freedoms that would have been unimaginable during the four decades before the uprising, but which are mitigated by instability and sporadic violence.
While Tripoli can go for days without disturbances, turf wars between heavily-armed rival militias can explode into gunfights within seconds, while regional tensions that were suppressed under Gaddafi are now dangerously exposed.
Last week's storming of an election office in the eastern city of Benghazi by armed protesters demanding greater powers for the region showed not only how far Libya has to go to foster national unity, but also underscored the real risk of unrest on voting day.
"The Libyan authorities should not make the mistake of underestimating their ability to disrupt the political process," the International Crisis Group think tank said of such protests, arguing that eastern demands for greater autonomy must sooner or later be addressed.
The weakness of the police and the army was demonstrated only last month when militia fighters occupied the runway at Tripoli's international airport for hours after they mistakenly feared their leader had been seized by security forces.
Yet while such incidents will do little to encourage potential investors in a country with Africa's largest proven oil reserves, many observers argue that Libya has bounced back from the conflict more quickly than expected.
Oil production has recovered and is now close to pre-war output levels of 1.6 million barrels per day. The country has also avoided the sectarian violence which sees dozens of Iraqis killed each week almost a decade after the U.S-led campaign to oust Saddam Hussein got underway.
"The basic elements of life are continuing in Libya," U.N. envoy Ian Martin told Reuters in a June interview.
"When you put it in the context of Libya and in the context of other post-conflict countries, the glass is half full rather than half empty," he added.
However, many Libyans remain baffled by the mechanics of Libya's first national multi-party poll since a 1952 vote held under King Idris, the post-independence monarch deposed by Gaddafi and a group of young army officers 17 years later.
The 200 seats in the new General National Congress will be allotted according to a mixed system, with candidates on party lists elected by proportional representation and independent candidates chosen by a simple majority.
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.
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.
Elections after Arab Spring uprisings that ousted dictators in Tunisia and Egypt have ushered in parliaments dominated by long-suppressed Islamist groups. Libya's polls will show whether political Islam continues its post Arab-Spring rise.
"Libyans will profess that Islamic principles are important and that they would only support someone whose values they share," said Eurasia Group.
But it suggested their commitment to political Islam had yet to be tested and was unclear: "Few Libyans express envy, for example, for the populations of Sudan, Iran or Saudi Arabia."
(Writing and additional reporting by Mark John; Editing by Andrew Osborn)