Mauritanians are voting for the first time since the country gained independence from France in 1960.
The 62-year-old is standing down after serving the maximum two five-year elected terms.
However the status quo is likely to prevail when a new leader is elected.
Abdel Aziz has expressed his support for Mohamed Ould Ghazouani, who is a former general and defense minister.
At least 9 killed in hotel fire in India's Kolkata
At least nine people have been killed, including a child, in a fire at a hotel in India's eastern city of Kolkata on Wednesday, local police said.
Ebola cases in Congo exceed 5,000, government data shows
The number of confirmed Ebola cases in the Democratic Republic of Congo now exceeds 5,000, government data has showed late on Tuesday, as health officials warn that response efforts are failing to contain the deadly disease.
8 Israeli airstrikes hit Syria's Abu al-Duhur airbase, state TV reports
Eight Israeli airstrikes have hit the Abu al-Duhur military airbase in northwestern Syria early on Tuesday, targeting the runway and storage facilities, Syria's state-run Ekhbariya said, citing a military source.
Indonesia earthquake death toll rises to 70, government aid arrives
The death toll from the powerful 7.7-magnitude quake that struck Indonesia last Saturday has risen to 70.
China's torrential rains kill 10 in southwest as thousands evacuated
Torrential rains have killed 10 people in China's southwest following a house collapse and a landslide, state broadcaster CCTV said on Wednesday, with tens of thousands also evacuated as a precaution.
