Tunisian voters poured into polling stations to vote on Sunday in their country's first free election, 10 months after vegetable seller Mohamed Bouazizi set himself on fire in an act of protest that started the Arab Spring uprisings.

The leader of an Islamist party predicted to win the biggest share of the vote was heckled outside a polling station by people shouting 'terrorist,' highlighting tensions between Islamists and secularists being felt across the Arab world.

Bouazizi's dramatic suicide, prompted by despair over poverty and government repression, provoked mass protests which forced President Zine al-Abidine to flee Tunisia. This in turn inspired revolts in Egypt, Libya, Yemen and Syria.

Rachid Ghannouchi, leader of the moderately Islamist Ennahda party, took his place in the queue outside a polling station in the El Menzah 6 district of the capital.

'This is an historic day,' he said, accompanied by his wife and daughter, both wearing Islamic headscarves, or hijabs. 'Tunisia was born today. The Arab Spring was born today.'

But as he emerged from the polling station, about a dozen people shouted at him: 'Degage' French for 'Go away,' and 'You are a terrorist and an assassin! Go back to London!'

Ghannouchi, who spent 22 years in exile in Britain, has associated his party with the moderate Islamism of Turkish Prime Minister Tayyip Erdogan. He has said he will not try to impose Muslim values on society.

'Islam should be respected again in Tunisia,' said Hasna Ben Zid, a 38-year-old woman wearing a hijab, 'That's why I'm going to vote for the only Islamic party.'

But the party's rise worries secularists who believe their country's liberal, modernist traditions are now under threat.

Across Tunisia, queues stretching hundreds of metres formed outside polling stations from early in the morning for an election which could set the template for other Middle Eastern states emerging from the Arab Spring.

That level of voter interest was never seen during Ben Ali's rule. Then, only a trickle of people turned out for elections because they knew the result was pre-determined.

People in the queues took photographs on their mobile phones to mark the occasion. Kamel Jandoubi, head of the election commission, said turnout exceeded all expectations, though he did not give any figures.

'This is the first time I have voted,' said Karima Ben Salem, 45, at a polling station in the Lafayette area of central Tunis.

'I've asked the boys to make their own lunch. I don't care ... Today I am not on duty. Or rather, I am on duty for my country,' she said.

There were long lines of voters too in Sidi Bouzid, the dirt-poor birthplace of the Tunisian revolution and Mohamed Bouazizi's home town.

'It's the first time I've voted because it's the first time I feel my vote is safe,' said Sara Naji, a secondary school teacher. 'We suffered a lot from pessimism and frustration but now we're building a new life.'

Sunday's vote is for an assembly that will draft a new constitution to replace the one Ben Ali manipulated to entrench his power. It will also appoint an interim government and set elections for a new president and parliament.

Most forecasts are that Ennahda will not have enough seats for a majority in the assembly, forcing it to seek a coalition which will dilute the Islamists' influence.

It will have to compete with secularist parties, who will try to form a coalition to stop Ennahda forming a majority.

Ennahda has been at pains to assuage the concerns of secularists and Western powers. Yet observers say there is tension inside the party between Ghannouchi's moderate line and more vehement Islamists among the rank-and-file.

A final election rally on Friday illustrated the party's contradictions as Suad Abdel-Rahim, a tall, glamorous female Ennahda candidate who does not wear a veil, addressed the crowd.

But many books on sale on the fringes of the rally were by writers who belong to the strict Salafist branch of Islam. They believe women should be segregated from men in public and that elections are un-Islamic.

'I'm not so optimistic about the result of the vote,' said Ziyed Tijiani, a 26-year-old architect who had just cast his vote. His forefinger was stained with the blue ink used in polling stations to stop ballot fraud.

'I think the Islamists could win. It's not want I want. They may try to change the way I live,' he said, accompanied by a young woman in jeans and T-shirt.

An Ennahda victory would be the first such success in the Arab world since Hamas won a 2006 Palestinian vote. Islamists won a 1991 election in Algeria, Tunisia's neighbor. The army annulled the result, provoking years of conflict.

Ennahda's fortunes may have a bearing on Egyptian elections set for next month in which the Muslim Brotherhood, an ideological ally, also hopes to emerge strongest.

Tunisia's election will be watched too in neighbouring Libya, which plans elections next year after a revolt there ousted Muammar Gaddafi.-Reuters