A moderate, once-banned Islamist party in Tunisia was on track Tuesday to win the largest number of seats in the first elections prompted by the Arab Spring uprisings, according to partial results.

The Tunisian electoral commission said the Ennahda party has won 15 out of 39 domestic seats so far in a 217-member assembly meant to write a new constitution. Together with the results announced Monday from Tunisians living abroad, Ennahda now has 24 out of 57 seats total, or just over 42 percent.

The final results from Sunday's elections could boost other Islamist parties running in elections in North Africa and the Middle East.

Ennahda, which was long suppressed by Tunisia's dictator before he was overthrown in January, was the best organized party in the election and had claimed victory Monday based on preliminary estimates, estimating around 30 percent of the seats.

The next most popular party, the Congress for the Republic, is a distant second so far with just 10 seats.

The results of the domestic seats were from 726,000 voters from five of the 27 electoral districts inside Tunisia and included the large cities of Sfax and Sousse.

An estimated 90 percent of the country's 4.1 million registered voters flocked to Sunday's polls, which have been praised by international observers.

"The voting process was marked by peaceful and enthusiastic participation, generally transparent procedures, and a popular confidence about Tunisia's democratic transition," said a statement by the Carter Center, which observed the contests.

Results, however, were being released in a trickle. Election officials said the painstaking nature of the counting process has caused the delay.

"The mechanism for tallying requires a lot of effort and time because all the votes in a district are taken to one place and this is for security reasons," said Boubker Bethabet, the secretary general of the election commission.

He added that, in many cases, poll officials sealed the tally sheets inside the ballot boxes after the initial count in the voting stations. The boxes can only be reopened in the presence of representatives of the more than 80 political parties involved in the vote.

(This version CORRECTS Corrects erroneous number of seats, updates with more details, official quote, Carter quote, adds byline, background.)