Results from polling stations across Mauritania began to trickle in Sunday but the electoral commission said it wasn't in a position to give an early picture of nationwide trends.
The commission said counting had been delayed in many regions where people were allowed to cast their ballots after the official deadline, adding that definitive results from Saturday's election would be made available "perhaps in the middle of the week".
State television has put the turnout at around 60 percent, a figure that, if confirmed, would severely undermine a campaign by a large swathe of opposition parties calling for a boycott of the polls.
A handful of polling stations have published their results, however, indicating a large lead for the ruling Union for the Republic and improved results for three opposition parties that did participate, Islamist group Tewassoul, the People's Progressive Alliance of parliament leader Messaoud Ould Boulkheir and El-Wiam.
The three announced they would join the boycott to highlight voting "irregularities", including 600 people in one Nouakchott constituency being unable to find their names on voter lists, if a second round were required.
Around 1.2 million people were eligible to vote in the first parliamentary and local polls since 2006, a test of strength for Mohamed Ould Abdel Aziz five years after he came to power in a coup and four years after he won a widely contested presidential vote.
Some 1,500 candidates from 74 parties representing the administration and the so-called "moderate" opposition contested 147 seats in parliament and the leadership of 218 local councils.
But Tewassoul was the only member of the so-called "radical" opposition, the 11-party Coordination of Democratic Opposition (COD), to contest the polls after its coalition partners said they would "boycott this electoral masquerade".