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 hits five Iranian oil tankers after attack on Navy ships
The United States has destroyed five Iranian oil carriers on Tuesday after the Islamic Revolutionary Guard Corps (IRGC) targeted its navy warship with ballistic missiles "twice over the past two days".
UK flights resume after major air traffic outage but airports warn of more disruption
Flights from British airports resumed early on Wednesday after a major air traffic control failure, but hubs warned that it would take time for operations to return to normal and questions mounted about the reliability of Britain's aviation systems.
Jordan intercepts 18 Iranian ballistic missiles
Jordanian army forces have intercepted 18 Iranian missiles targeting the country early on Wednesday.
Air traffic control issue disrupts flights at major UK airports
Flights at major British airports were disrupted on Tuesday by a technical fault at air traffic control provider NATS, the latest in a series of failures that renewed questions about the resilience of Britain's aviation infrastructure.
At least 73 injured after Houthi rebels attack Saudi civilian and energy facilities
At least 73 civilians have been injured after Yemen's Houthi rebels attacked a number of civilian and energy facilities in Saudi Arabia's southern region on Tuesday, state media confirmed.
