The "Yes" camp has secured a large victory in Mauritania's referendum on a new constitution, which would set limits on presidents' time in office.
Mauritanian voters have never changed their leaders
With all but one area reporting, 97% of voters backed the changes, with a 76.5% turnout, the interior minister said.
The referendum was organised by the military junta which seized power in a bloodless coup last year.
Its leader, Colonel Elly Ould Mohamed Vall, has promised to organise free and fair elections, and to leave power.
Mauritania - a desert state that straddles Arab and black Africa - has never seen a change of power come through the ballot box.
Presidents limited to two consecutive terms
Terms cut from six years to five
Maximum presidential age limit of 75 imposed
Observers from the African Union and the Arab League backed the vote, noting a "good atmosphere" and a "strong mobilisation of voters".
"It is a historic day for Mauritania. It is truly the rebirth of politics in this country," said Col Vall, after casting his vote in the capital, Nouakchott.
Oath of office
Under the new constitution, presidents could only serve two terms in office - each of five years, instead of six.
Heads of state would have to swear not to change the law on presidential terms when taking their oath of office.
Several African leaders have sought to overturn two-term limits in the constitution - some have succeeded, while others have been blocked.
Mauritania's latest military strongman has promised change
The junta which seized power in Mauritania in a bloodless military coup last August overthrew an unpopular government, which had been in power for 20 years.
At first the international community condemned the latest military coup but it is now watching with interest to see if the reforms are followed through.
Col Vall - a former intelligence chief - says he will not stand in the presidential elections, which are due to be held next March assuming the constitution is adopted in the referendum.
Mauritania is a chronically unstable, extremely poor country with Arab tribes that often show more loyalty to their chiefs than to the state.
Black African Mauritanians say they are oppressed by marginalisation and even slavery.
One of the African political parties has called for a boycott of the referendum saying it does not address inequalities in the country.
Although Col Vall's reforms seem to have marked him out as very different from previous military leaders, veteran opponents of the government say they are disappointed he has not investigated allegations of corruption against former governments.
A few days before the vote, the authorities said they had arrested a group of people connected with the government overthrown last year. They were accused of plotting to destabilise the country.