Only 43 parliamentary seats were filled in the polls on Novermber 19, making a second round, held on Sunday, necessary to decide the remaining 52 seats.
The elections were the first since Maaouiya Ould Taya, the former president was overthrown in a bloodless coup last year.
Taya had ruled Mauritania for 21 years and was accused by opponents of rigging elections even after bowing to pressure to allow political opposition in the 1990s.
The current military government deposed Taya and came to power while he was attending the funeral of Fahad bin Abdul Aziz al-Saud, the former king of Saudi Arabia.
A new constitution, which ensures that no president can serve for more than a decade, was approved overwhelmingly in a referendum in June.
Colonel Ely Ould Mohamed Vall, the head of the military government, says he will give up power after senate elections in January and presidential polls two months later.
Consequently, parliament will not sit until after a March 2007 presidential election.
The military government had barred its members from taking part in the country's elections in order to guarantee transparency.
Spanning Arab and black Africa, and bordering Algeria, Mauritania is a US ally.
Its strategic importance has also been enhanced since it started pumping crude oil in February, and as a focus for efforts to stop African migrants leaving its shores for Spain's Canary Islands in the hope of a better life in Europe.