The mainly-Muslim republic, a former French colony on the west coast of the Sahara desert, is seen as strategically important in the fight against Al-Qaeda-linked groups within its own borders, as well in neighbouring Mali and across Africa's Sahel region.
"I think these elections today are a victory for democracy in my country," President Mohamed Ould Abdel Aziz said after visiting his local polling station in Nouakchott.
Around a third of Mauritania's 3.4 million people are eligible to vote in the first parliamentary and local polls since 2006, a test of strength for Abdel Aziz five years after he came to power in a coup and four years after he won a widely contested presidential vote.
Some 1,500 candidates from 74 parties representing the administration and the so-called "moderate" opposition are registered to vie for 147 seats in parliament and the leadership of 218 local councils dotted across the shifting sands of the vast nation.
The process of voting appeared more complicated and arduous than had been expected and long queues began to build up outside polling stations in the capital.
Towards the end of the morning many stations were tripling the number of booths available for casting ballots.
"I came in the early morning, I have just voted. There was a long wait but I have done my duty," said an elderly woman at a Nouakchott polling station.
Party activists near several polling stations discreetly tried to canvas last-minute support, breaking election law.
"I know propaganda is forbidden near polling stations on election day, but everyone is doing," said a campaigner called Rabia when challenged by a journalist.
