Morocco's vote was the first since the approval of a new constitution in a July referendum that transferred some of the monarch's near absolute powers to parliament and the prime minister.
Under the new constitution the king, the latest scion of a monarchy that has ruled the north African country for 350 years, must now choose a prime minister from the winning party instead of naming whoever he pleases, as in the past.
The Justice and Development Party (PJD) captured 107 seats in the 395-seat assembly in Friday's polls, according to final results released by the interior ministry on Sunday. "The results are better than we expected," PJD leader Abdelilah Benkirane told cheering supporters at the party's headquarters in Rabat, Morocco's seaside capital, after the results were announced.
Benkirane may meet with the king on Tuesday to be nominated prime minister, said PJD parliamentary bloc leader Lahcen Daoudi. "Abdelilah Benkirane could be received at the palace tomorrow (Tuesday) to be officially nominated," he told AFP.
"Benkirane will then start talks with the parties that should make up the coalition."
The monarch proposed changes to the constitution as autocratic regimes were toppled in nearby Tunisia, Egypt, and Libya as part of the Arab Spring uprisings and pro-democracy protests brewed at home.
The PJD election victory comes less than a month after a moderate Islamist party won Tunisia's first free election and ahead of a predicted Islamist surge in Egyptian polls that got underway Monday.
"The PJD ready to govern," said business daily L'Economiste said on its front page Monday. "The test of power," said free daily newspaper Aufait, under a photo of Benkirane with a broad smile.
An Islamist party has never been allowed in the government. Since the PJD will have to govern in a coalition with several other parties, it is not expected to make radical changes to policy.
The 57-year-old Benkirane, who sports close-cropped white hair and matching beard, has acknowledged that his party would have to tailor its programme to appease its coalition partners.
"But the nub of our programme and of those who will govern with us will have a double axis, democracy and good governance," he told France 24 television on Saturday after partial results showed his party had won the biggest block of seats.
The PJD captured just eight seats in the first election it contested in 1997, but has since surged in popularity. It scooped 42 seats in the 2002 election, the first of Mohamed VI's reign, and then increased its share in 2007 when it finished second with 47 seats.
The party initially focused on social issues, such as opposition to summer music festivals and the sale of alcohol, but has shifted to topics with broader voter appeal like the fight against corruption and high unemployment.
In the latest campaign, it promised to cut poverty in half and raise the minimum wage by 50 percent. The election was originally planned for September 2012 but the king brought the vote forward to create a new government that could put in place the constitutional reforms.
Voter turnout was 45.4 percent, up from 37 percent from the last parliamentary election in 2007, but lower than the 51.6 percent turnout recorded in 2002.
Morocco's pro-reform February 20 protest movement, responsible for protests held just before the king announced plans to change the constitution, had called on voters to boycott the election. It argues the reforms do not go far enough.