The ruling El Insaf or Equity party scored a comfortable win in the first round of elections, gaining 80 of 176 parliamentary seats.
The political parties which backed the Mauritanian president won 36 seats, while 24 went to the opposition. Nine seats were taken by the conservative Tewassoul movement, the main opposition party in the out-going legislature, which favors a strict application of Islamic law.
El Insaf also won all 13 regional councils and 165 of 238 local constituencies.
In the run-off poll scheduled for Saturday, May 27, voters will choose members of parliament for the remaining seats in several electoral districts.
The elections were the first since 2019, when President Mohamed Ould Ghazouani came to power.
The main opposition parties – including the Rally of Democratic Forces, the Union of the Forces of Progress party, Al-Sawab (The Right Path) and the National Rally for Development – said they have recorded major violations in what they call a "heavily manipulated" vote which they termed as "an electoral farce marked by systematic fraud in most regions of the country."
Zainab Mint al-Taqi, a major opposition candidate, said the opposition agreed the elections were "marred by violations."
She said among the irregularities were a delay in opening many polling stations and the refusal by some centers to allow the entry of party representatives.
According to the Middle East Monitor news site, the opposition said that the voters' registration list had been tampered with, and that some voters were registered in areas to which they did not belong - and did not reflect their political preferences.
Observers also said the sorting process was slow, in part because of the need to respond to opposition claims of irregularities.
The opposition, which has formed a high-level "crisis committee" to follow developments, is calling for the results to be annulled in several areas, including the town of Boutilimit and the capital. Nouakchott.
However, Muhammad Taqi Allah al-Adham, the spokesman for the Independent Election Monitoring Authority, denied any violations of the polling and counting process.
Maryam Mint Lamoud of the El Insaf party said that as an observer, she did not come across any alleged violations. "Our party as well as all other parties were given equal opportunity without any favor for the ruling party," she said.
The African Union, sent a mission to monitor the elections, headed by ambassador Calquiste Aristide Mbarre, an official in the department of Political Affairs, Peace and Security, to monitor any breaches. The A.U. has not yet issued any statements regarding opposition complaints.
Some observers say the results provide a boost for Ghazouani and his chances to win a second term in next year's presidential elections.
He has overseen the West African country's relative stability in the increasingly violent Sahel region, and is widely expected to seek re-election in 2024, although he has not confirmed his plans.
Some information in this report came from Agence France-Presse