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.
US military says it turned away blockade runner trying to reach Iranian port
The US military has announced that it fired a missile into the engine room of a vessel trying to get through the US blockade of Iran on Friday.
WHO chief urges safe burials in visit to heart of Ebola outbreak
The World Health Organisation (WHO) chief has travelled on Saturday to the Congolese province hardest hit by an Ebola outbreak, urging residents to seek treatment and practice safe burials as officials scramble to contain the fatal disease.
Rescuers pull four from flooded cave in Laos
Rescuers pulled four people from a flooded cave in Laos on Saturday, Thai volunteers said, hours after another man was brought out late on Friday.
Brazil investigates suspected Ebola case in Sao Paulo
Health authorities in Brazil's Sao Paulo state are investigating a suspected case of Ebola reported on Saturday in the state capital, officials said.
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