TRIPOLI - Acts of sabotage, mostly in the east of the country, prevented 101 polling stations from opening on Saturday in Libya's first post-Gathafi election, the electoral commission's chairman said.

"Ninety-four percent of polling stations opened," Nuri al-Abbar told reporters in Tripoli, with voting underway in 1,453 out of 1,554 centres.

"Some of the polling stations were not opened. Because of security reasons, logistical materials haven't reached them," he said.

"We are currently dealing with this, sending material to the polling stations so they can start voting," stressed the commission chief.

The remarks came just five hours after the start of voting.

The commission, he said, was considering extending the deadline from 8:00 pm (1800 GMT) to midnight in voting centres affected.

Libya's elections for a General National Congress mark the first national poll after four decades of dictatorship under slain leader Moamer Gathafi, who was toppled by a popular revolt last year.

"The turnout was excellent despite the high temperatures," Abbar said, noting that the preliminary figures of voter participation were being compiled.

He said the polling process for Libyans abroad was going "smoothly."

Most of the disruptions were concentrated in the east of the country, cradle of the 2011 uprising that overthrew Gathafi and heartland of factions that have threatened to sabotage the landmark election.

Hundreds of protesters burned ballots to demand greater representation although most residents of the Mediterranean city of Benghazi voted on Saturday.

Gunfire echoed after around 200 demonstrators filled a major square in the eastern city, which was the cradle of last year's revolt that ousted leader Moamer Gathafi.

They were encircled by cars of supporters of the vote for a national assembly and later by at least a dozen military vehicles whose forces fired into the air in a show of strength.

But as soon as the armed forces left, the protesters began to attack the civilian cars, damaging several of them.

"We are the ones who started the rebellion and now nobody is bothered about us. Nobody wants to talk to us. All we are asking for is a proper democratic process," said one demonstrator, who gave his name as Fuad al-Obeidi.

"Let the constitution be written first then hold the elections with equal number of seats for every region. I have boycotted the election along with my family," the 32-year-old government employee said.

Abduljawad Shadwan, a 49-year-old lecturer who supports the election process, condemned the protesters.

"I can understand their views but this is not the right way. We are building a new Libya and actions like these only deny the building of a new country," said Shadwan.

"But this will not stop the progress of Libya. The result of the election will be unprecedented. It will be historic," he added.

Elsewhere, gunmen attacked a polling station at Tulay Tala School in Benghazi Jadida in the city's southwest, destroying the ballot boxes and firing into the air before fleeing, according to witnesses.

"Around 60 men and some women stormed the school at around 1:00 pm (1100 GMT) before breaking the ballot boxes and stealing some election material," said Ahmed Saleh, an election observer at the school.

"Some armed men fired in the air. Some bullets hit the school building, shattering the glass. They were chanting 'Allahu akbar' (God is greatest)," he said.

Earlier, voting was marred by attacks by protesters calling for greater representation at one polling centre in the city and some other parts of eastern Libya.

They forced the closure of several polling stations in areas outside Benghazi, but failed to dampen the enthusiasm of most of the city's residents to cast their ballot.

Benghazi was the first city to rebel against the regime of Gathafi, with protesters, inspired by the Arab Spring uprising in neighbouring Egypt and Tunisia, pouring out onto the streets in February 2011.

That initial protest in Libya's second-largest city spread rapidly to engulf the entire country. It ended with the capture and killing of Gathafi on October 20 after a revolt supported by powerful NATO air cover.

On Saturday, groups of young men carrying machineguns were patrolling various streets, especially near polling centres, offering what they said was "protection to voters and voting centres."

But protesters forcefully closed several polling stations. Some voting centres were shut in the eastern city of Ajdabiya, where a depot containing electoral material was torched earlier this week, an official in Benghazi said.

Another official said voting was disrupted at oasis towns in southeastern Libya, including Jalo and Ojla, after federalism supporters prevented a plane carrying polling material from taking off.

Abdeljawad al-Badin, spokesman of the self-appointed Cyrenaica Council, said voters in Quba, near the town of Derna, were boycotting the electoral process altogether.

Interim leader Mustafa Abdel Jalil, who voted in his eastern home town of Al-Bayda, said "we hope that our brothers in Benghazi will stay away from such problems and that the voting will go ahead as planned."