Story highlights The Arab Spring started in Tunisia

The longtime ruler was overthrown in January

Seats are up for grabs in a National Constituent Assembly

Tunisians who live overseas have begun voting in an election billed as the freest and fairest since the country's ruler was toppled earlier this year.

Polls open on Sunday in Tunisia and it is considered the first election of the Arab Spring, the catchphrase for the political discontent that started in Tunisia and then spread across the Middle East and North Africa.

Tunisia's election commission said Tunisians in Australia began voting in Canberra and Tunisian Afrique Presse news agency said expatriates are to begin voting on Thursday in Canada.

Candidates are competing for 218 seats in a National Constituent Assembly, which will be charged with writing a new constitution and probably deciding the structure of Tunisia's future government.

Zine el-Abidine Ben Ali, the strongman who ruled Tunisia for nearly a quarter of a century, was overthrown by street protests last January.

More than 60 political parties are competing in the contest, as well as thousands of independent candidates.