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.
New Lebanon-Israel talks begin in shadow of US-Iran deal
Lebanon and Israel began a new round of talks on Tuesday in Washington, with Beirut determined to press ahead with direct negotiations even as they appear to be overshadowed by Iran's decision to make Lebanon part of its talks with the US.
EU hosts Taliban officials in Brussels for first time
A delegation from Afghanistan's Taliban met on Tuesday with EU officials in Brussels for the first time.
US waives Iran sanctions, Trump warns Tehran it must abide by agreement
The United States waived sanctions on Iran for 60 days from Monday after the first talks under a nascent peace deal, with US President Donald Trump saying he will "do what I have to do" if Iran does not stick to its side of the agreement.
Forty drown in France as people seek relief from heatwave
Forty people have drowned while swimming in unsupervised areas in France since the weekend, the prime minister said on Tuesday, as people tried to escape a heatwave sweeping across much of Europe.
Israeli gunfire kills two people in south Lebanon, civil defence says
Israeli gunfire killed two people in southern Lebanon on Tuesday, Lebanon's Civil Defence and state media said, the first reported fatalities resulting from Israeli fire in Lebanon in three days.
