* Ennahda party wins 90 seats in 217-seat assembly
* Violent protest in birthplace of uprising
* Election is first in wake of "Arab Spring" (Adds Ghannouchi saying currency will be made convertible)
By Tarek Amara and Christian Lowe
TUNIS, Oct 28 (Reuters) - The leader of the Islamist party which won Tunisia's first free election appealed for calm in the town where the "Arab Spring" began, accusing forces linked to the ousted president of fanning violence there.
Party officials said coalition talks were already under way and they expected to form a new government within 10 days.
Troops fired in the air on Friday to disperse a crowd attacking government offices in Sidi Bouzid, where 10 months ago vegetable seller Mohamed Bouazizi set fire to himself in a protest that ignited revolts around the Arab world.
The Ennahda party, which was banned for decades and its leaders forced to flee abroad, will lead Tunisia's new government after an election victory likely to set a template for other Middle Eastern states rocked by uprisings this year.
Ennahda has tried to reassure secularists by stressing it will not impose a Muslim moral code.
It will not impose the wearing of the Islamic headscarf, or hijab, on women because all attempts to do that in other Arab states have failed, the party's leader said on Friday.
Rachid Ghannouchi said women would have jobs in the new government "whether they wear a veil or don't wear a veil".
Ennahda would honour an undertaking to finish writing a new constitution within one year, he said at his first news conference since the election. It would respect all Tunisia's international treaties when it forms a new government.
He blamed the Sidi Bouzid clashes on forces connected with ousted president Zine al-Abidine Ben Ali.
The unrest was not linked directly to the Ennahda win, but to the fact that a party headed by a businessman popular in the town, a former supporter of Ben Ali, had been eliminated from the ballot over allegations of campaign finance violations.
UNREST IN TOWN OF "MARTYR"
Two witnesses in Sidi Bouzid told Reuters a large crowd had tried to attack the local government headquarters.
"The military are trying to disperse the people with shots in the air and tear gas," one of the witnesses, Attia Athmouni, said by telephone.
The witnesses said shops and schools were shut and a security forces helicopter was hovering overhead.
Late on Thursday, after officials announced they would cancel several seats won by the Popular List, a crowd set fire to an Ennahda office and the office of the mayor. The party had been running in fourth place in the election, according to preliminary results, before its seats were cancelled.
An Interior Ministry source said a night curfew would be imposed in the town from 7 p.m. (1800 GMT) until 5 a.m.
Ghannouchi paid tribute to the town's role in the revolution which forced Ben Ali to flee the country.
"We salute Sidi Bouzid and its sons who launched the spark and we hope that God will have made Mohamed Bouazizi a martyr," said the Islamic scholar, who spent 22 years exiled in Britain.
Announcing the results, election commission members said Ennahda had won 90 seats in the 217-seat assembly, which will draft a new constitution, form an interim government and schedule new elections, probably for early 2013.
The Islamists' nearest rival, the secularist Congress for the Republic, won 30 seats.
TURKISH PM IS MODEL
The complex election system that replaced the rigged, one-horse races conducted before the revolution made it impossible for one party to win a majority of seats. Ennahda is expected to form a government with two of the secularist runners-up.
The Islamists have already said they will put forward Hamadi Jbeli, Ghannouchi's deputy and a former political prisoner, for the post of prime minister. Jbeli said on Friday the economy would take priority in coalition negotiations.
"We are going to speed up to build the new government," he said. "It will take between a week and 10 days."
Ghannouchi told Reuters in an interview he would pursue a liberal economic policy, including making the dinar currency convertible.
Ennahda lies at the moderate end of the spectrum of Islamist parties in the Middle East. Ghannouchi models his approach on the that of Turkish Prime Minister Tayyip Erdogan.
His officials say there will be no restrictions on foreign tourists -- a big source of revenue -- drinking alcohol or wearing bikinis on the country's Mediterranean beaches.
The victory is the first for Islamists since the Hamas faction won a Palestinian election seven years ago.
It will resonate in Egypt, where a party with ideological ties to Ennahda is expected to do well in a multi-stage parliamentary poll that starts in November.
One of the party's most prominent candidates is a businesswoman who does not wear the Islamic veil, or hijab, and this week sang along to pop songs at a party rally.
Ennahda has also reached out to anxious investors by saying it will not impose Islamic banking rules. It says it is inclined to keep the finance minister and central bank governor in their posts when it forms the new government. (Additional reporting by Abdelaziz Boumzar; Writing by Christian Lowe; Editing by Andrew Roche)