Moroccan election officials are counting votes after Friday's first parliamentary election since the king introduced constitutional reforms.
Around 45 per cent of registered voters turned out to cast their ballots, Moroccan Interior Minister Taib Cherkaoui said late on Friday.
International observers described the turnout as "satisfying" in comparison with 2007, when only 37 per cent of eligible voters went to polls.
Voting stations closed at 7pm (19:00 GMT), with the first provisional official results expected several hours later. Final results are expected to be announced on Saturday.
On Saturday, the Islamist opposition Justice and Development Party (PJD) said it had won the largest number of seats in Morocco's parliamentary election on Friday.
"Based on reports filed by our representatives at polling stations throughout the country, we are the winners," Lahcen Daodi, second in command of the party, told the Reuters news agency.
"We won Rabat, Casablanca, Tangier, Kenitra, Sale, Beni Mellal and Sidi Ifni to cite just a few."
Government officials could not immediately confirm the party's claim.
Overall 31 parties are vying for the 395 seats in the lower house of parliament, 70 more than during the last election in 2007.
Sixty of the overall parliamentary seats are reserved exclusively for women, and 30 seats for young people.
Friday's polls were the first under a new constitution proposed by King Mohammed VI and approved in a July 1 referendum amid popular uprisings in nearby countries.
Opinion polls are not allowed in the North African country but observers said the PJD was likely to win the largest number of seats.
The party's main rival is the Coalition for Democracy, a loose eight-party pro-monarchy bloc that includes Finance Minister Salaheddine Mezouar's National Rally of Independents party.
The PJD had expressed concern that the elections could be rigged to keep it out of power, but Italian observer Matteo Mecacci told journalists there was "no indication" of fraud. About 4,000 national and international observers were present to ensure transparency.
The amended constitution gives more powers to parliament, government and the prime minister, who now must be appointed by the king from the party that wins the most assembly seats.
Morocco's king responded to pro-democracy demonstrations this year by amending the constitution and bringing forward parliamentary elections by a year.
Analysts said a high voter turnout would give credibility to the reform of the constitution approved in a July referendum.
Activists, however, still agitated for a boycott saying the reforms were not sufficient.
While the constitutional reform transferred some of the king's powers to parliament and the prime minister, the monarch retains full authority over the military and religious affairs and still appoints ambassadors and diplomats.