Aziz, who led a coup against the government last August, had 52.2 percent of the vote with rival Messaoud Ould Boulkheir garnering about 16 percent of the vote, Radio France Internationale reported. Ahmed Ould Daddah, the head of the main opposition party, was reported third with about 14 percent of the vote.
Aziz relinquished control of the military junta in April and resigned from the army to become a candidate in the election.
Some voters Sunday complained of being registered in cities where they didn't live and of erroneous numbers on registration documents and identification cards, RFI reported.
Poll watchers from the African Union, the Arab League and the association
of Francophone countries were in Mauritania for the election.
An estimated 61 percent of eligible Mauritanians voted out of a total population of 3.2 million people, officials said.