There are fears of renewed violence in Libya amid the country's first elections since Colonel Muammar Gaddafi was toppled.
An electoral worker was killed on Friday as campaigning came to an end when gunmen fired at a helicopter carrying voting material for the polls.
The helicopter was forced to make an emergency landing outside the eastern town of Benghazi. It was not immediately clear who was responsible.
Saturday's elections, which will see a 200-member transitional parliament formed, caps a tumultuous transition from last year’s civil war.
Col Gaddafi's death brought a close to the uprising, but the end of his four-decade rule left the country deeply divided along regional, tribal and ideological lines.
The parliament will elect a new transitional government to replace one appointed by the National Transitional Council (NTC), the organisation that led the rebel side during the eight-month war and held power in its aftermath.
However, tensions have been brewing as many in Libya's oil-rich east have express anger at the NTC-issued election laws.
Although they are said to be based on population, the rules allocate their region less than a third of the parliamentary seats, with the rest going to the western region that includes Tripoli and the sparsely-settled desert south.
In what it called an attempt to defuse the row, the NTC decreed on Thursday that the new parliament will not be responsible for naming the panel that will draft a new constitution.
Instead, the drafters will be directly elected by the public in a separate vote at a later date.
But this has not satisfied some in the east, who press for a boycott.
"We don't want Tripoli to rule all of Libya," said Fadlallah Haroun, a former rebel commander in the east's regional capital, Benghazi.
Friday's helicopter attack was the latest in a string of violence in the run-up to the vote.
On Thursday, ex-militiamen shut down three eastern oil refineries - in Ras Lanouf, Brega and Sidr - to press the transitional government to cancel the vote, Mr Haroun said.
He said militiamen also have cut the country's main coastal highway linking east to west.
Earlier this week, ex-rebel fighters and others in Benghazi and in the nearby town of Ajdabiya attacked elections offices, setting fire to ballot papers.
Saturday's vote is expected to test the strength of Islamist parties, which have gained influence in Libya and other nations after dictatorial regimes have been toppled.
Some 2.8 million voters, out of more than three million eligible, have registered for the polls. New parliamentary elections are to be held in 2013, after the constitution is drafted and approved in a referendum.
Observers expect that no party is likely to win an outright majority and the final government may be based on post-election alliances.