Police in Mauritania on Thursday fired teargas to disperse opposition members who were protesting against a referendum to be held on Saturday.
Opponents say the vote would pave way for President Mohamed Ould Abdel Aziz to seek third consecutive term
The Police intervened as demonstrators opposing the constitutional amendment met in the west of the capital, Nouakchott.
The riot took place less than two hours to the start of a meeting in which President Abdel Aziz had promised he would make an important announcement.
The amendment of the constitution, which the radical opposition considers illegal, provides for the abolition of several institutions, including the Senate which would be replaced by regional councils elected.